My builders grade Whirlpool oven has become very uneven over time, both side to side and front to back.

I have had to pull to pull the oven out from time to time to replace the thermostat control (4 times), I'm just adding this in case it's important. I have not used the self cleaning in some time, for obvious reasons.

What can I do to relieve this problem, even if only temporarily until I can afford a new, hopefully higher quality, wall oven.

Thanks a lot!