Hi Mello; If the reverb works when the amp isn't disturbed, chances are the problem isn't electronic ... it's mechanical. You might try taking the reverb can out and looking at the connections to the transducers and the connections between the transducers and the springs. Also, see if the springs seem to have too much travel; they're are supposed to be suspended so they can move around a little but maybe the little springs that restrain them have lost their tension.
You might also look at the plug/jacks at the reverb can and amp; they may not be snug enough to withstand getting bumped; if they are too loose, they can send the 'reverb-send' tube section into oscillation. Incidentally, if you have a working polarity switch that actually does something, then you probably have a two-wire power cord; if so, that power cord needs to be replaced with a 3-wire cord.
If all else fails, you could try scolding it and shaking your finger at it ... instead of saying 'bad doggie' ... say 'bad amp'. :wink: If that doesn't work, you can always give it the finger but most professional techs agree that hostility rarely works. Good luck with it.