The white stop post shouldn't be what triggers the flop it just holds the ball and can be turned off. The optos right at the top of the ramp is the trigger so you might make sure they are clean.

Here's the whole set.
https://www.marcospecialties.com/pinball-parts/802-5000-88

Was the mounting screws for your VKU hitting the side rails and causing the top of the VKU tub to hit the glass?

Is it just me or does the aluminum angle piece behind the center 4 drop targets seam like a crappy afterthought? Seams like there’s got to be a better way to do that...

The other drops have wireforms behind them. I assume the aluminum L was added to ensure a ball couldn't hop over a wireform and get trapped, but there are three holes that look like they could be for posts. I think I'm going to try putting three posts there and see how that works. I think the posts could cause the ball to bounce erratically when hit instead of just SDTM everytime.