I'd only try running through the VCR if you have to have the VCR power on to do it, in other words, if the signal will be sent through an amplifier stage.

This sounds funny, but you might open 'er up if it isn't too hard, blow things out, and look to see if there is any obvious problem with one of the capacitors. It sounds like somebody is changing when they get hot. Does this continue when it starts, or is it just intermittent? That would be a clue if it is a thermal thing or not.

There may be some variable inductance you can play with in there, they will likely be tall, square components with provision for turning a slot on top with a tiny screwdriver. You may be able to move an active component into a more stable part of its operating curve that way, but how do you tell, unless you have him on a scope? Wish you were here.

Having said all that, I'd smack it first, just to knock any crud off the components. Lots of times, ya' get lucky that way.

-Chuck, Vegetarian fanboy