as long as the wood is not warping enough to twist the pcb longitudinally , it should be fine.
but any amount of pcb Twist is very bad.
I don't think there's really any twist happening with the PCB itself or the plate, but now you have me a bit worried so I took a closer look.
The more I look at it the more I think that the frame isn't really warped, it just seems like sort of a wonky cut/sanding job on that edge. All of the other edges are nice and straight, so I tried to take a couple pictures of it (excuse my crappy cell phone camera) to show what's going on. Obviously not the most scientific method but I threw a grid on there as well to help show how the caps and by extension switches sit in relation to everything else.
The total height difference between that right front corner and the other three is less than a millimeter. Two index cards sitting under it is all it takes to stop the wobble, but I don't want to risk damaging my board in the long run so I'll defer to your judgement.