This reminds me of TAF, where the ball would derail off the cross-playfield wireform when the transition between the end of the plastic ramp and the rails wasn't perfect. I don't think any switch would provide enough force to knock the ball off the rails here... really looks like it's rattling a bit as it comes off the plastic ramp into the wireform channel. Did tightening that screw change anything? Perhaps the ball is hitting the back rail (high rail towards back of game) as it exits the ramp and rattling rather than dropping in the channel cleanly...

Yep, same issue as TAF. There has to be a smooth transition from the plastic wall to metal rail, otherwise fast-moving balls are doomed. Could be your plastic ramp was slightly deformed and pulling it closer to the wireform helped mitigate the issue. Glad you're up and running!