I have the same problem. It's not that the values don't change, it's they keep going back to the same number. You can often see the real number by buying in the sticker shop.
In what I think are related issues, two other things keep happening that started around the same time...
First, my character challenges keep showing me ones I've already completed and it can be difficult to figure out what to concentrate on because of it. Like the coins, it goes back and forth between the old and current values.
Next, a free character pack I received for leveling up keeps showing up again and again and again. I've opened in 3 times individually, then after one game there were actually 3 of the same pack waiting (seemed like all 3 of the packs I'd had opened previously just showed up again).
PS. Made my own post on the issue, but accidentally put it in the xbox sub-forum instead. Anyway to get a mod to delete it? Didn't see the option for myself to do so.
(http://answers.ea.com/t5/PvZ-Garden-Warfare-Xbox/PvZ-Corrupt-account-data-in-game/m-p/4561012#U4561012)