SO, I finally figured out the opto/crane/trough/multiball problem so many of us have been having ( Mancave most recently). Or, if nothing else, I got us another step closer to figuring it out.
Initially, I thought it must be the troughs, so I fixed, then replaced those. No dice.
Then, months ago, I (thought I) solved my problem by re-soldering the crane opto connections, but I think what actually happened is I must have physically moved the optos further out, causing them to trigger fully.
Recently, it has been having the problem again (multiball ending early, next ball firing out too many balls, etc), and, fed up, I spent a lot of time fiddling with it and came up with the solution of physically moving the optos further out to cause them to trigger sooner. I think the issue is that the optos do not fully trigger when the ball is passing through (despite them successfully triggering in tests), thus causing it not to register. I have no idea why this works, but it works.
TL;DR: If your JD ends multiballs early and then kicks out too many balls, it may be time for you to put a ring on it (or 40, in my case...10 small washers on each screw, and longer screws).
20171012_145305 (resized).jpg