Check your Steps setting. On the website, go to Apps->Steps. On the app, go to Steps. Make sure it is set to "Fitbit Tracker". You'll still probably need to manually delete the extra adjustments. I had a duplicate for yesterday and I deleted both adjustments and then added a 1 calorie cardio exercise in MFP to force a recalculation, then deleted the added exercise.

There is an app server the app talks to - which then talks to the account server the web and your dongle talks to.

Account server talks to Fitbit.

So the fact the app shows different than web view is not unheard of - just means slow syncing between app and account server, and then to your app.
People have seen stats actually on the device that synced to mobile app - app displays some the same, some different. And then web view to account shows correct stats. Eventually the app gets the stats back again and updates.
But it appears very wrong - and may be Fitbit taking some stats and doing corrections on them. Like if you updated weight it changes your base burn and daily burn - but if that didn't sync to device yet, it has wrong figures. So that is correct type of syncing - the delay just makes it look bad.

I think the multiple adjustments is unrelated and different bug.