Greetings campers, here's some more data. I have all three Avenger pins with the Hulk still in the box, the blue in the basement and the pro on location (I have Marvel issues). The first time I played the LE in the basement right out of the box I saw this problem and it crops up pretty regularly on my pro on location. Its ok if it does it to me but doing it to customers is a bad thing. Here's my findings last night when I dug into this.
As many people say above, if the ball drops into the saucer right as multiball starts the ping pong game starts EVERY TIME AND THIS IS A REPEATABLE PHENOMENA ON BOTH OF MY MACHINES (sorry for shouting). Software version 1.4 on both. I tried the soft coil setting to no effect. Wait a few seconds to start Hulk multiball and it doesn't happen so that aspect of it is DEFINITELY A SOFTWARE ISSUE.
On my Blue LE:
1) I noticed that every time the ball hit the H drop target the bridge would rattle so it was hitting the bridge as well.
2) Just for giggles I lifted up the bridge by hand and started the ping pong game again and the even though the H target still "double tapped" the ball was able to make it through. Problem sort of solved but not really as its just a work around.
So I went back down to my location where a guy that I had just had to give a refund (and a collector) was still there and we dug into the pro.
On the Pro:
1) Again we were able to perfectly repeat the issue every time with witnesses.
2) I was able to lift up the left side of the Black widow ramp assembly a few millimeters by hand and the ball was able to fight its way through when starting ping pong mode.
3) There is a post in the middle of the left side of the BW ramp assembly with a washer on it and I was able to remove the screw and raise the BW ramp assembly a few millimeters by putting it on top of the washer.
4) With the BW ramp assembly raised up just a bit on this post the ball can fight its way through in ping pong mode.
5) The bad news is now that BW ramp has a single point support instead of a multi-point support and it wobbles.
6) I gave a lot of credits to a guy for play testing and it didn't seem to affect the flow (much) on the BW ramp. Its kind of a bitch to hit anyway.
7) Now I have to figure out how to make additional shims/supports for the BW ramp for my pro on location.
I may be totally screwed on my Blue LE as I'm not sure I can do a similar "lift job" on it but will investigate. My Blue LE is scheduled to go out on location soon and I need to run this to ground.