Any chance there’s a static electricity element? There have been reports of folks with dust collectors having to bond systems together to prevent restarts. Perhaps a little extra grounding could keep you running.
you can do the same by just using a self-tapping screw to attach a piece of wire on each end. The screw will protrude into the vac-hose and provide a place for the static to discharge. It saves a lot on copper for those with long vac runs.
Can you wrap the controller in something that can be grounded? When I put my DIY controller box together I used sheilded cables and an old repurposed plastic enclosure. I added some aluminum tape to the inside of one side of the box so the shields landed there and then connected that tape to the ground line of the IEC connector bringing the power in. So far, I haven’t seen any static issues.
Awesome setup! Your CNC build for making surfboards sounds impressive, especially the table adjustments and spindle setup. For the freeze issue, check for firmware updates or interference. Adding ferrite beads to cables might help.