Hi lasik2025,

I was busily reversing engineering a 3-axis controller when another user 'doorknob' pointed out your existence over on this forum page.

Here's some more flaws for the list.

- There is a FR301 diode in the motor voltage supply to each TB6560. When back EMF hits, that current can only dump into the 3300uF decoupling cap. The volts increase and folks on this forum start practicing their French. >> replace the 3 culprit diodes with fuses.

- No back EMF diode on the coil of the relay >> add diode

- Pins 25 of the TB6560 extends over the trace from pin 23 >> trim back

- Heatsink not grounded. The resistance from heatsink to ground is small but non-zero. When failure occurs substrate currents will help the remaining TB6560s to join the party >> according to the datasheet isolate each device from the heatsink or simply ground the heatsink

On the OSC pin issue, I observed a nice sawtooth waveform, ranging from 0.5V to 2.5V, with a frequency spread from 38kHz to just slightly over 40kHz.
The max step rate for the TB6560 is 1/4 of this.