Quoted from MK6PIN:Are you using drop dead foam at the top of the form? Works way better than stock rubber.
That piece pretty much solved for me...got the trough loading correctly about 95% consistently w some tweaking as well...just some thoughts..
I had a rubber stop from TAF in my shelves and replaced the black original rubber stop with it. Works very well now. I believe it is this one: https://www.marcospecialties.com/pinball-parts/23-6702