MAMEWorld Forums - Ultimarc - JPAC issue with Screw Terminal connectors

Here's one that's bugging me that I've tried to debug and isolate, but can't figure it out.

With my new JPAC, anything connected to the screw terminals will stutter when held down. You can see this in notepad very clearly: kkkkkkkkkkkk-pause-k-pause-kkkkk-pause-kkkkkkkk (the pauses are brief). It appears that it stops sending/receiving for a moment.

I say this, because if I try to have one used as a shift key, it loses the shifted status. For example, I have me ESC shifted with Start-P1 to become Coin-P1. It will go from 5's back to 1's (MAME keys), and intersperse 5's and 1's.

I have isolated the ground, tried just one input on it, made sure it was on the same ground as the JAMMA, with no effect. 4 of the player buttons are on the same ground as the JAMMA, and 3 admin buttons are on the screw terminal ground, with no difference. I've tested the grounds with a voltmeter to see if there is anything with that, and it zeroes out.

Now, on the JAMMA side, it is perfect. Repeats as normal and no stuttering.