I’ve this setup:
Arduino controls 3-phase contactors, through optoisolated relays array (powered separately).
Arduino is not on the same box as contactors (1 meter away).
When it starts/stops few of them (or I start/stop some of them manually) characters on LCD get corrupted.
This happens randomly.
As far as I can sense it is some kind of interference, but I did not manage to find anything on forums.