G540 Failing...not faulting

So may setup is this Old PC running XP, Mach3 to the Parallel Port to the G540. From the it's CNCRouterParts, Nema 23's and cables. I'm using a 48V 10A power supply to power the mess.

The setup used to work. I stopped using my CNC a couple years ago, and found some new uses for it lately. So after about 4 years of non-use, I powered it back up and all was well. I ran 6 toolpaths successfully at around 8 minutes each.

Then....mid toolpath, it stopped. Grinding noises. All Axis. This is what I've found:

Set the estop, PSU has 48V. Reset the estop, and move an axis for 2-3 seconds normally, it stops suddenly, make noises, PSU is now 11.11V. Will not move unless estop is set and reset.

It's repeatable. I isolated to one stepper and tried it on all ports of the G540 and manually jogged. Same result, but the voltage is 12.5V upon stalling.

The G540 is always in the green(with the exception of the etsop). I've taken it apart and checked the inner G250 boards, they visually appear fine, and checked continuity on each between PINs 1-4 with everything, no continuity with anything except the final ground.

I ave a new 48V 12.5A powersupply coming in tomorrow, but are there any red flags for specifically known problems here??

Thanks you guys for any help you can offer!