Resistor failing is more likely to a symptom, rather than the cause.

Replacement VFD is the cheapest option. Chances are some of the internal drive mosfets/scrs/whatever they use will have blown, possibly along with drive circuitry, so unless you have lots of time to spend trying to diagnose/test, a new VFD is the path of least resistance.


I'd check wiring to the spindle, for internal breaks. I'd also measure the three phases/coils of the spindle, and check they're all similar resistance. Also test each pin to earth, in case the spindle has shorted internally.
Not using water may have caused the spindle to overheat, damaging the internals. If you have access to a megger/insulation tester, it would be worth testing each coil against the earth pin, and spindle body for any insulation failures.

I'd suggest replacing the wiring with some proper shielded cable, as that just looks like standard flex, which may be the source of the failure, as it won't withstand regular flexing like a CNC spindle does.