I don't have a direct 1:1 action->result yet, just something that occurs intermittently.
When uploading firmware via DWC, any connected serial terminal application (Pronterface, SerialTools) will crash with a verbose stack/IO error related to the app (so, not especially informative). This behavior is inconsistent and I've been trying to update to a non-beta 3.2 firmware to eliminate this as a cause but have been unable to (see posting in firmware).
It's not a fatal problem, subsequent application start and connection will succeed. Since the HW is new, seemed worth reporting. Let me know if I can collect more data.