I believe this could be the thread for anyone in the future. My MPCNC made in China - #176 by forcerouge
Specifically post 186 describes the problem I’m having:
Only the firing phase seems to pose problems, if I never release the switch between different paths, then it continues to cut perfectly fine.
Extremely similar to my problem, except my Arduino seems to completely reset when the arc starts. It forgets what g-code file is loaded in cncjs. I’m hopeful that some power wiring changes that I’ve just done might make it better.