Ok, I took this thing out.
I cleaned the bulb and the hole it peeks through. It seemed pretty clean already as in the picture. I fired it up, but it still stops. Your description is perfect, it's just as if the stop button is pressed.
EDIT: Ok, I can't get it back in so for diagnostics I put the slider all the way at the end. It seems to be playing fine now. So is the switch broken?
EDIT: OK, I put it back in. The VCR seems to be playing fine now. I'll let this thread know what happens.
If it still misbehaves, how can I clean the slider sensor? That seems to be the cause. Deoxit?