Great write up. I may do this in the future. Are you in the US of A? Midwest?
The 2800 (Sears) so far is the only system that I can get to do it. When you say early 6 switch is that only the heavy sixers or the light sixers as well? I have a light sixer sears (2600) I might try with the Tac-2 to see if it exhibits the same issue. Interestingly the 2800 came out after the 4 switchers (I think? could be wrong) so you would think they would have made the fix on it as well.
I just tried Berzerk on the 2800 with a Wico Command Control and it initially created the same signal bounce, except it's much more subtle, but only when using the button on the base (not the white button on top). Actually as I played longer it seemed I was unable to reproduce the signal bounce and it worked perfectly, although when I initially turned the console on it was extremely obvious and the button actually didn't work consistently. The controller has been in a garage or somewhere dirty and almost assuredly hasn't been used for 20 years (not sure, just bought it) so maybe there was some dirt or corrosion in the microswitch that was causing the issue that became dislodged as I used it.