I was thinking that I need to test the relay circuit isolated from the rest of the PCB, but I've done that before, it works. I know I should test every circuit when components change, but they are both 5V relays with the same current requirements for the coil to trip the relay. "Murphy's Law" gets me every time.

I'll try your ideas when I feel motivated about this again.

I have a 10k0 between 5V and MCLR. I am making a CNC Mill "Monitoring PCB" between Mach3, the software controller on a PC, and stepper-motor driver hardware, and I assume software. I've oscilloscope-tested the 12kHz signal, which according to Mach3 is suppose to be 12.5kHz, and it is a good 0V to 5V square wave. The PC DB25 signal is stepped up from 3V by a three-state octal bus transceiver.

Anyway, I'll let you know if your suggestions help.