unplugging it from the power input.
after each time I've disconnected the boards it worked for a day, on the next day it started doing problems again.
The issue could certainly be a bad connection due to thermal expansion or possibly a power supply issue.
You seem to suggest that you've already replaced the caps on the power supply boards, is that correct?
Do any of the boards which you disconnect from the power supply contain BGA package devices?
As you mentioned, "baking" a board is often the homebrew remedy for thermal expansion connection issues, however it is far from a perfect remedy and could certainly be the cause of additional issues to arise.
Heating a board up to a temperature to permit solder reflow is a particularly delicate procedure, maximum time intervals must be observed, so as to not damage other components on the board. It's particularly difficult to successfully reflow a BGA package device's solder balls, which may require specialized equipment to target only the BGA package device itself.
Typically, faulty display driver boards manifest their symptoms visually on the screen when powered up, irregular lines, numerous stuck pixels, waviness of the picture, etc.
Replacing the entire suspect board, particularly if the board has BGA package devices maybe the only sure remedy.
However, that being said, if the entire system powers down, particularly after being powered up for a period of time and there is a lack of visual irregularities mentioned above, such symptoms often indicate an issue with one of the power supply boards, it could be a bad connection or a faulty component which is thermally sensitive.
BigDog