nuisance hard limit alarms

I recently put limit switches on my machine, and now I continuously get nuisance hard limit alarms. It's got an Arduino controller running GRBL .9. I used shielded wire for the switches, and ran the wires well away from all the power wiring. I first noticed it when an infrared motion light in my garage turned on, I got a hard limit error. So, I put in a good AC power filter on the laptop and control electronics supply. Seemed to correct the problem - for a while.

Then, last night I...

nuisance hard limit alarms