I found the capacitors on the IF strip could cause the intermittent signal or low gain problem. The coating on the capacitors extended down the legs.
when I re soldered the panel I would ease the capacitors backwards a little this would usually cure the problem.
The picture ballooning problem was not too bad on a correctly set up chassis but was always present to some degree.
In their defence though they were fairly cheap compared to other makes at the time...
Rich