From my experience it is a gpu that is 100% hung and prevents the miner from restarting without a power cycle or a gpu reset. I do this automatically in my bat script using DevManView.
Devmanview bat
@echo off
echo.
echo *** Restarting GPU
timeout /t 2 /nobreak >nul
devmanview.exe /disable_enable "Radeon (TM) RX 470 Graphics"
echo.
echo *** DoNe