Infinite scanning by defender

When I scan my site from the Dashboard, Defender tells me to wait 'a few minutes'. Make that a few hours. But arriving at 25.01% after 3-4 hours he scan stops, there is no progress anymore.
First I assumed it lost connection, so I restarted and BINGO, again at the same percentage it stopped.

My site is protected by CloudFlare, don't know if that might be relevant.