Happens all the time on the MM on route near me. Pretty lame and it does happen a lot.

I always felt that the troll head assembly should have had a piece on the back that would set flush with or just above the playfield to prevent it from happening, but I don't think there is.

Not sure about the one near me, but a google image search for "medieval madness pinball trolls" shows quite a few touching the rail. The IPDB picture with the raised trolls might be as well, but the image isn't at a great angle for determining that. The MMR promo flyer also makes it look like it's touching the rail, or very close to it.

I'd just roll a couple balls down the wireform at different speeds and make sure they're not catching or hitting the edge of the raised trap door.

Congrats on the new game, by the way!