External E-stop requested in Mach III when there isn't

[kemlin]

The spindle on my machine will run for around 10 seconds and then Mach III states there was an external E-stop.  I have watched the PMDX126 and the E-stop light does not come on.  I checked ports and pins for E-stop function and my manual switch works.  I have debounce set to 400u to eliminate (or help with) noise interference.  Not sure what to check from here.  I did some reading on the dip switch settings and moved 7 to open.  What should I be checking for?

[Steve Stallings]

The most common source of this type of problem is electrical noise generated
by a VFD or brushes in a DC spindle motor. Try running without turning on the
spindle to verify if this is indeed the source of the problem.

Things to try:

If it is, and you are using a VFD, try using a shielded cable from the VFD to
the spindle and ground the shield to the Earth or safety ground terminal on
the VFD.

Keep power wiring to and from the VFD as far from other wiring as possible.

Try a "common mode choke" near the VFD output and possibly on the input.
All three wires of 3 phase must go through the same choke.

http://www.pmdx.com/VFD-Choke

Try even more debounce in software.