The idea was to have the transistors in stock, should not be expensive. Yes, not a good idea to replace components randomly, but replacing a transistor or two around the problem area is reasonable.
Never had a problem with the spray being conductive. It was years ago when I used the stuff at work, was a standard fault finding method.
It will probably be fine as it is.
Wait until it is varying, use freezer spray on transistors until you find culprit?
It varies without any warm-up time, straight from switch-on, or if the unit has been on for a while, so not sure changes in temperature would show any fault/cause, but I'll give it a go.
I think you'll find it will!