That's a Shimano SPD knockoff from Taiwan. I don't know if that's a good or bad thing, but I suspect it's a bad thing.
First, clip both shoes into the pedals, then remove your feet from the shoes. This is a pretty good opportunity to hurt yourself, make sure nobody is recording it for a Youtube video.
Second, using both hands, one at the toe, one at the heel, unclip the left shoe from the pedal. Then unclip the right one. If it feels the same, and you used the same motion both times, try to clip them back in by hand and repeat a couple times until you are sure.

Assuming they both feel the same, it's not the mechanism. If they are different, there is an adjustment screw that makes it easier or harder to clip out of the pedal. You should set them to "very loose" since you're new to clipless and not confident with them.

Again, assuming they feel the same, it looks like the sole of the shoe could rub/get caught on the pedal as you try to release. This could be from putting pressure on the outside edge of the show, dragging the heel, hard to tell without seeing it.

When you go back the LBS, have them put the bike on a trainer so you can "ride it" without risk of falling over. Practice clicking in and out, don't leave until the problem is solved, or at least identified.

All that said, good pedals are expensive, and I respect that bargain brands are a good way to start with most bike accessories, but being able to click out reliably is extremely important to you, and your safety. If you can't upgrade to a set of better pedals, ask the LBS to replace the cleat on the shoes with a real Shimano cleat, if it fits, it may work better. It's quite possible the fault is with a cleat that is malformed.

Be careful about moving the cleats around on the shoes, small angles and small changes fore/aft can play havoc on your knees and hips. A good bike fitting is also expensive, usually starting around $150, but the difference in comfort and joint health is worth many times that. At the very least, google "bike fitment" so you can get the bike close to correct for you.

Good luck,
Dale

Found this article


by Jim Langley

Please note: This article is about positioning bicycle cleats on cycling shoes. If you are looking for information on how to install and remove pedals, please go here.

The balls of the feetA good neutral starting cleat position that works for most riders is to place the cleats so that when the shoes are clipped into the pedals, the balls of the feet are directly over the center of the pedal axles (also called the pedal "spindles").

It can be tricky to locate the exact ball of your foot and place the cleats so that the balls are directly over the pedal axles. Note that the ball of the foot is defined by Biology-Online.org as “the padded portion of the sole, at the anterior extremity of the heads of the metatarsals, upon which the weight rests when the heel is raised.”

So, if you stand with your bare feet fully on the ground they touch at the heels, the balls of the feet and the toes (assuming you're not completely flat-footed). And, if you stand on tip toes, you are standing mostly on the balls of your feet.

Again, you should position your cleats to center the balls of your feet over the center of your pedals axles (see diagram).

Here's an easy way to get it right

1. With your shoe nearby, and with bare feet, place a dot of paint or a drop of whiteout (correction fluid) on the center of the ball of one foot. If you can't see the bottom of your foot well enough to do this accurately, have someone help you.
2. Immediately, so that the paint or whiteout doesn't dry first, slip on your shoe, close the straps and stand to put pressure on your foot.
3. Remove the shoe and you should find the paint dot transferred to the inside of the shoe clearly marking the ball of your foot. Repeat steps 1, 2 and 3 with your other foot.
4. You can't see the dots on the insides of your shoes from the outside when you're positioning the cleats so use this workaround: simply stick a straight pin through the side of each shoe (the side next to the crankarm). Make sure the pin exactly bisects the mark inside the shoe and sticks straight out of the shoe, not at an angle. Now, when you flip the shoes over to position the cleats you will have a pin in each as an indicator telling you exactly where the cleats needs to be positioned to put the balls of your feet directly over the pedal axles (note that you could also look at the pins and paint a line on the shoe soles if you prefer). Usually centering the cleats over the pins will be the right spots to center the balls of your feet right where they should be directly over the pedal axles.

Exceptions
Try the ball-over-the-pedal-axle position first and give it a chance to see if it feels right because it works for most riders. If it doesn't feel right, the most common adjustment to make it feel better is to move the cleats back slightly, perhaps 1/2 inch. This puts a little more of your foot over the pedal. This is often preferred by larger riders with longer legs, people who push bigger gears, climbers and time trialists, riders using long crankarms and slower pedalers.

Conversely, if you tend to ride at a high cadence, spin smaller gears, like sprinting, ride shorter crankarms and are a toes-down pedaler, you might move the cleats forward slightly, but don't overdo it. Maybe about 1/4 to 1/2 inch (about 6 - 10 mm). If you get too far out on your toes you increase the risk of "hot foot" and even Achilles injuries so experiment but only a little at a time.

Lastly, if you're an ultra-distance rider you may want to push the cleats all the way back. This type of riding often causes numbness and hot foot. A great solution discovered by long-distance champ Lon Haldeman is moving the cleats fully to the backs of the slots, which relieves pressure on the feet and has no negative side effects for this type of riding, apart from a slight increase in the possibility of toe overlap with the front wheel if you're riding a bicycle with aggressive front-end geometry.

Angle adjustment
Most clipless systems include some "float," the ability of the cleats to move slightly so that you will automatically find a natural angle to hold your feet when pedaling. However, it's important to get the cleats close to the right position when mounting them. If they're angled incorrectly there might not be enough float in the system to allow you to correctly position your feet, which could result in pain when riding or even a knee or foot injury. It can also make it harder to get in and out of clipless pedals.

A good neutral starting position that works for most riders places the cleats so that when the pedals are mounted in the shoes there is space between the heels of the shoes and the crankarms that's about 3/4 of an inch (2 cm), or about the width of an average man's index finger.

If you experience any discomfort when cycling that's associated with your cleat position, I recommend visiting a shop with an experienced cleat fitter and paying a professional to dial-in your position.

Two tricks that help some riders: If you adjust your cleats carefully and still find that your ankle(s) is too close to the crankarm and sometimes brushes it (or worse), a simple fix is to place an automobile spark plug washer(s) between the pedal(s) and crankarm(s). The washer will slip right over it, not effect the threaded connection to the crankarm and provide several mm of clearance.

If you need more clearance, a great solution is SCOR Productions’ KneeSavers. These are custom pedal extensions that allow you to add 20, 25 or 30mm between your pedals and crankarms. You can read all about them and place an order here. A reader also told me about this generic version of these extenders available on Amazon.com (photo, right).

Mark the position
Once the cleats are perfectly positioned on your shoes be sure to mark them so that when they need replacement it's easy to find the perfect position. Some shoe soles have marks on them for this and some cleats come with marking stickers, etc. Or, you can just trace a line around the shoes in indelible ink. Or try a gold paint pen for carbon-sole shoes.

More tips
Be sure to lubricate your cleat bolts before installation, which will ensure you can get them tight enough to remain tight. And, be sure to check the bolts/screws after a few rides to make certain they are remaining tight.

If you keep a spare set of cleats on hand you will always have them if the cleats on your shoes become too worn or they break. Spare cleats also come in handy for comparing with your used cleats to determine if they're worn enough to replace them yet.

Speaking of cleat wear, you might look into rubber covers for your cleats, which are offered by a few companies. You carry them on rides and slip them over the cleats when you stop for protection and for additional traction when walking. Here are the ones I use:

Be sure to keep your clipless pedals and cleats lubricated where they meet each other to prevent clicks and creaks. A good cure is the car-care spray Armor All, which you can find in any hardware store. This works on plastic, carbon and metal cleats/pedals.

This sounds similar to issues I had with a pair of Shimano 105 SPD-SL pedals I had years back. 2 other people I knew bought the same pedals within a week or two of me and we all had release issues with them. Even on the lowest tension they wouldn't release for anything and after >1 year of using clipless prior to the SPD road pedals I was falling at least once/ride because I was unable to unclip...painful and embarassing. I returned them and switched to LOOKs and had 0 issues. I've never had issues with Shimano mtn. pedals, either.

+1 on the Speedplays here as well. I have Zeros on both road and TT bikes. My wife had a lot of the same kinds of complaints the OP does, i.e. trouble unclipping one side, with SPD pedals. I finally convinced her to try Speedplay Light Actions and she's hooked. She loves them, and no more problems.

I have these:

http://www.amazon.com/Shimano-PD-M780-XT-Race-Pedal/dp/B008K7LR3Y

And I know, "support your local bike shop" but trust me, I support them enough. I don't feel guilty ordering a few things online.

If money permits do not be afraid to hold onto your old pedals. Pedals are something that having a spare set kicking around is not the worse thing in the world

Hmmmm. Few years back, I broke my leg due to a failure to uncleat from a freakishly stiff SPD pedal. I'm gonna check to see if they were Shimano 105 SPD-SLs (might have been). Grrrr.

I really love my Speedplay Light Actions on my road bike. So easy to clip in/out and lots of float. Just wish they weren't so "delicate" (always losing a cafe cap & replacing worn cleats). It's just the nature of the design. I still love them - they're worth the "fuss".

Pepper, any progress?

This reminds me, I need to adjust the tension on my left pedal. I had one of those couldn't get the foot out of the pedal at the stop sign moments on Monday. Even after hitting the ground hard, I still had trouble getting the foot out, so I could get up. (Of course there were people watching!) Fortunately, nothing broken, just some nice, colorful bruises on my left wrist.