Installed a pin2dmd in my TSPP and it looks awesome ( got the files from previous poster who colored the frames.... great job).
Had quite a few issues with ball movements ( be kind ) under the mini playfield. Ball rarely reached the up-kick and when it did it mostly failed to sense.
Replaced u-switch (for the 3rd time... crap switches) with a self formed hoop switch and this part working very well. Ball binding caused by several factors.
1. wiring loom drooping down and ball rubbing on it as it passed through.. well tried to anyway.. easily sorted.

thought a-ha... done... not so fast.

2. subway switch, just behind garage door not allowing full movement in relation to micro-switch lever causing it to slow ball and in most cases stop it.
so changed the lever/actuator interaction to allow gate to swing fully up allowing ball to pass through either way depending on speed.
no further issues and I am enjoying getting back to this deep masterpiece of Stern code completion.

Upgraded from V4.0 game and display rom to V5.0 (for both). Sorry didn't try pin2dmd with V4.0 as I guessed the key frame differences might be an issue at times. Also updated pin2dmd to latest Vers. think it's up to v2.47.

I think you are on the right track.

Have both machines, playing the TSPP a lot more ( but I only recently got it back after on loan for 8 months ), play my MM way more than either of the others though..

I disagree, power sounds fine as does the rom since it is doing exactly what it's designed to do. It is now waiting for data from the cpu board. Check your ribbon cable between you cpu and display pcb. Check for corrosion on your cpu pcb under the batteries. even reverse/rotate the dmd data cable ( must do both ends ), this will use different wires in the cable and possibly change the symptoms..

Good luck.