A similar error appears on startup or in a debug log:

A fatal error occurred.  PIVX can no longer continue safely and will quit.

EXCEPTION: St13runtime_error
tinyformat:Too many conversion specifiers in format string
C:\Program Files\Pivx\pivx-qt.exe in Runaway exception



A bug in the code for invalidating fraudulent zPIV spends



Update to v3.0.5.1 or newer.  If you have problems syncing, follow the instructions in the link