And BTW, I've had this thing in the garage, during the summer, with AC full blast and the doors open for 20 mins and could not recreate the issue - tested it the same way after driving awhile and it did happen again.

Thinking the temp sensor, check a hose under the hood with an infrared temp gun both before and after issue to ground truth your onboard temperature measurements. Can get an infrared temp gun at Harbor Freight pretty cheap. I've got 2017 V60 with random overheating issues, but different symptoms. O...