OTA update + USB serial connected = hard fault on Photon

Doesn’t always happen, but happens often enough I need to unplug USB before updating firmware.

Conditions:
USB connected to win 8.1 PC running teraterm. No serial data being received by Photon - only being transmitted every 15 secs or so.
SYSTEM_THREAD(ENABLED);
SYSTEM_MODE(SEMI_AUTOMATIC);

I’ve seen other odd behavior too, such as really long delays before the OTA update happens, weird patterns of magenta (on 5 sec - off 5 sec for what seems like a minute), issues with getting a stack overflow on OTA update.