Woodwork project - dealing with a timber crown

[moustachebandit]

I have been building a hidden cupboard at the end of my hallway. The idea is that once its done you wont know its there, until you press on the panel and it pops open.

Things have been going really well I have made the carcass and paneled it and I have also constructed the door.

The issue I have now is that after a few days in the house it appears that the timber I was using for the door frame has bowed slightly which now means that the door wont sit flat with the walls as has a belly in the middle - essentially ruining the hole hidden door idea. I have got one side panel on the door already and the door has bowed on the side that doesn't have the panel attached. Could this be the reason why?

Does anyone have any good ideas on how I can correct this?

Thanks