Check the math MFP is using to calculate your adjustment. (Go to the exercise page and click on the little 'i' next to the adjustment.) I've had intermittent problems with this. When it happens to me, I have two adjustments instead of one. One won't show me the math and can't be deleted. The other one will show me the math but the MFP calories burned number is wrong. I sent some screen shots to MFP customer support last week but I have been too busy to follow up.

I reported the problem to MFP about a week or so ago. They asked for some additional information, but the message was sort of boilerplate so I didn't give it a high priority (I'd given them screen shots already) and didn't get around to responding. Yesterday they sent a message saying they thought they'd fixed it (I didn't see the email until this morning - I'm really behind on email) but I had it happen to me again yesterday, so I sent a reply telling them that.

It's really frustrating. I can go in and manually calculate what the adjustment should be, but don't know of a way to fix it since MFP is adding exercise calories that aren't there to the MyFitnessCalories Burned number. Instead, I fall back to using Fitbit's calories remaining number instead of MFP's. It doesn't work well early in the day, but that isn't when I generally have a problem. Later in the day, it's pretty close to what MFP would tell me.