Just kind of an update to this:
I started seeing this error more often when I started cleaning the bed surface with a combination of rubbing alcohol and Costco cleaning wipes, followed by Aquanet (purple can) hairspray for priming the surface, while it was preheating. I'm using a borosilicate bed surface lined with a thermal pad sheet. I heat the bed up to 90C for printing PETG, and it's intermittent. If I can reproduce this on a more consistent basis I'll keep you guys posted. I usually have a workaround of disconnecting the printer from MatterControl and reconnecting, continue to preheat, and so far the error seems to clear.