It's not something I've seen.
Ages ago when testing out an external USB enclosure that was not on UPS/isolated surge-protected socket I could get it to self-eject/disconnect from the NAS when I switched on/off a fan. Both were on the same power strip, but I think the surge-protection was only on the wall cable.
I can't remember what state it left the drive in, whether visible in some part of DSM or not, but the only remedy I found was to to physically disconnect the USB cable and re-attach.
Everything is on UPS now and I've not experienced this since.