Nickelplate759, if you are using "plastic rail joiners" that don't come up flush with the top of the rails, a metal wheel should drop into the gap and make an electrical connection across it. Kato rail joiners, for instance, only have the plastic spacer well below the top of the rails, so they don't prevent metal wheels from bridging the gap and making an electrical connection.
I've been using Atlas insulated joiners, and they fill the gap completely - and some of my gaps are a little big. Trimming them seems to help.
Here's what seems to have helped so far:
1. set trip current for PSX and PSX-AR to 1.27 A (CV49=1)
2. Enable delay for the PSX (CV55=1, leave CV65 at default).
3. Trip insulated rail joiners so wheels can bridge the gap.
But above all, ensure that your engines have good pickup and/or Keep-Alives. All problems are with engines that have less than stellar pickup.