It’s not as intended, but it’s a bug not a switch problem.
I believe the basic issue is that the ball is going by the magnet with enough speed that when it wants to engage, the ball leaves the opto, then gets sucked backed onto the magnet triggering the opto again. I’ll be suppressing the 2nd hit when the magnet is firing.
Dont know if its common knowledge, but on Stern Iron Maiden (premium), if you just started hallowed be thy name and already have lit mummy lock, shooting the left ramp will complete two hallowed shots in one: First the ramp shot, then when the ball is dropped into the mummy lock it will award the second hallowed shot which is the captive ball.
No biggie, but the more shots you get “for free” the better 
Does anyone know if this is a deep cut or a series of malfunctioning machines?
On Congo, I’ve heard two reports and I have also experienced that AMYs later in the game always divert to the volcano, making you shoot the left orbit from the right flipper instead of the easy loop shot. Can someone confirm or deny this?
I’ve seen this, too, but only when I’ve successfully completed Amy multiple times [I think it was after the third completion]. It would appear to be a programmed way of limiting exploitation of the Amy mode.
Owned a Congo and yes, after one or two completions (can’t remember which), you get all volcano feeds instead of easy staged loops to make it harder.
Could it just be after you’ve done a Super Multiball?
Ask and ye shall receive (somewhat). I streamed Congo tonight.
Played two Amy modes, and they both worked normally. Then played Super Multiball. My third Amy started diverting balls shot into the volcano out of the top of the volcano and back to the right flipper. Subsequent Amy modes worked the same way.
So, I guess I can’t say for sure if it’s the 3rd time, or after Super Multiball. Unless you’re going all out Amy, it’s pretty likely that you’d have played Super Multiball by the time you get to your third anyway.
Game starts here: https://www.twitch.tv/videos/543508159?t=54m47s
First Amy: https://www.twitch.tv/videos/543508159?t=56m45s
Second Amy: https://www.twitch.tv/videos/543508159?t=1h2m
Third Amy: https://www.twitch.tv/videos/543508159?t=1h13m10s
There was at least one or two other Amy modes, but they worked the same, so I’ll leave those as an exercise for the viewer.
I tested this last week and couldn’t get it to work…anyone else have success? (No time was removed at all)
On Batman 66, you can indefinitely freeze timers during the main (Villain) Multiball by shooting a ball into the Mystery for an award and then constantly shooting Jackpots. Mystery awards are a lower priority animation than the Jackpots, and all timers freeze until the Mystery award is collected.
Technically it can work for any Multiball, but Villain Multiball has longer Jackpot animations and more convenient ways to collect them (alternating ramps, left ramp to scoop, etc)
This also applies to ball-save timers, too, iirc. And also applies to many other recent Sterns (not necessarily just Mystery causing the Multiball ball-save timer freeze).
These are both also true - there’s a few games where this doesn’t apply (GotG on mode timers for example), while others don’t have the animations to exploit with.
Comboing out Villain Multiball (shots never un-light) is the peak version of the exploit that I’ve seen. “Add Time” provided an extremely long ball lock for legal single ball Multiball play as well as froze the Playfield X timer it was working on for way longer than 15 seconds!
Avoid starting the multiball on TAF, at any cost! Don’t break the flow/spell of ramp->chair, ramp->chair, ramp->chair, ramp->chair, ramp->chair, ramp->chair, ramp->chair…
On TAF you can no-switch drain when you’re plunging for the skill shot after locking a ball for multiball. On whirlwind, you will lose your ball if you try this.
I can’t remember the details on which ROM(s) this is possible but if you drain fast enough on CFTBL you will get an eternal ball save. Eg. an extra ball.
I used to plunge, get KISS and drain fast to plunge to get the PAID-letters. To save some time I started doing a so called “drop-insta-drain” to make the ball drain fast, to save a second or four (it’s, obviously, incredibly boring!). As far as I remember it doesn’t happen every time (might be related to how fast you can drain?) but sometimes the ball save continued to active the entire ball. Probably just on ball 1.
On KISS, Heavens on Fire and Hotter than Hell are (funny enough) an anti-stack: the KISS targets don’t reset until a Super Jackpot is collected.
All it took was this one use of the concept of “anti-stack”…and I already need another hit. Got any others?
(Not just things that don’t work well together, but things that would actively prevent progress).
DP’s Berserker Rage + (anything) 
I freaking hate when I have Sauron lit, but the game won’t let me play it because Berserker Rage gets in the way. I’d rather score points than score no points. 
The Munsters blocks you from Munster Madness if you’re in any other mode. Extra fun if you accidentally start Lily during your last mode.
Funny thing is berserker rage is probably worth more points!