As you say it’s likely to only be a connection problem. Probably when you removed the fascia/control panel I expect. But unless you can locate said fault the only option would be to send the display board and main module over for EMW to test.
The heater wasn’t damaged by the loose drum by any chance? 💡
If you are only getting half a display at normal brightness then I would guess that there is a dodgy joint on the display board – if you can’t see it then try flexing the board slightly when it has power and you may find that it flickers on/off.
I don’t have any display boards here to check with but I would guess that there are a couple of common grounds for the LCD and that it is one of these that is the problem.