Not sure about the switch being a common thing. I've never had an issue on my TZ. The diverter is a known issue. I bought a magnet years ago that someone used to sell. It fits in the gate and keeps the ball from bouncing out before it gets dumped. I guess you could call it a mod, but it's really just a week magnet that you tape in the gate.

Sorry didn't notice you had already considered the magnet.

I fixed my bounce-outs by reshaping the diverter cup box. It is square from the factory, so the left wall that the ball stops against rebounds the ball straight back to the right. So I reformed (bent) the shape of the left wall of the cup to lean ever so slightly to the right, like / , just not quite that far. This small adjustment makes the left wall rebound down into the rails instead of straight back up them. You have to play with it a little to get the angle right while keeping that flange that sticks out to the right from hitting the rails. Nothing else I tried worked as well as this solution.

YMMV

I have the exact same problem with my piano switch. Doesn't happen all the time but when it does I have to shake the machine from side to side which means I have to play with tilt disabled.Very frustrating. I tried the same fixes to no avail.
I was thinking about moving the switch further down the subway but not too keen on hacking the plastic. Is it possible to replace a micro switch with an optic switch? Let us know how you go.

Definitely get the magnet 'mod' for the diverter. The powerball is in play maybe 5% of the time. With the magnet I went from a fail diverter drop about 50% down to under 5%. Still happens occasionally but it's the exception now, not the rule. Much less frustrating.

Really with the powerball, how often does it end up in the diverter? And of those occurrences, how many fails? What I'm saying is don't pass on the magnet because it has no effect in PB.

Here's the one I got http://pinballpro.net/shop/twilight-zone-diverter-magnet-tz-dm/

I was having a bounce out issue and found that a weld on the wire form was broken near the mini playfield.

can't i share links about it?

The wireform might be nice and tight, but that doesn't mean it's aligned correctly.

My TZ used to have issues with the diverter not even activating, let alone dropping the ball properly. After some investigative tweaking and screw turning, I found that it was in a bind and out of proper alignment. Once I relieved that tension, got it into a nice set position, then locked it down there, the diverter has grabbed and dropped the ball perfectly every time since then.

Mine also has the magnet mod. It's a must, especially for my game since it's so fast. It really traps that ball in there well.

I will try to get it done tonight if I can remember...send me a PM re: this thread. That should work...