Topward 7020 problem, Help!

[GoldenGun]

So i recently bought a topward 7020 off of ebay for £50, when it arrived I turned it on and tested the cal point and the proper square wave appeared tho it was a bit dim on max intensity but a problem i noticed was that the waveform for ch1 only was jumping up and down the screen for no reason and moving the position knobs wouldn't stop it but this only happened to ch1 so I opened it to check for dust and grime even if the seller said it was dry stored for years I found some rust on the transformer and on a few screws but besides that everything looked good, no blown capacitors nothing so I took the board with the potentiometer on it off to clean it(I thought it was the potentiometer) so i used contact cleaner on it and put it back in then i closed the thing up and surprise now the waveform on ch1 and 2 didn't appear at all i touched the probe to the cal point, my finger, messed around with the coupling and the other stuff on the front but no waveform would appear  not even moving the knobs on the front would change anything besides the left right position, so i opened it up again to make sure i put everything back together properly and nothing seems wrong so I looked it up and found a person with a 2021 had a similar problem but going through the thread didn't show me anything that could help i checked the transformer voltages and it was all good, so I made this thread to ask for help.

[tunk]

Maybe bad solder joints disturbed when you took it apart?

[GoldenGun]

I wouldn't think it was solder joints since i couldn't get the board out fully all I could get out was mini board on which the potentiometer was mounted on and i made sure the solder joints and cable worked by continuity checking them.

[GoldenGun]

Update I managed to get a trace on the screen and now it displays the square wave but i still have the problem that the trace on both channels isn't stable it jumps around and sometimes doesn't want to display while doing so, any ideas?