I enabled Daily reporting on defender on 2 sites yesterday, and Defender all went well and scan started this morning as expected. Once it ran though Defender continuously scans, and seems to 'forget' the ignored files I had set.
This goes away when you change reporting back to Weekly.
This was on 2 sites on 2 different accounts. Do you know if this is an issue on defender? I found a post about something similar but the conversation just seemed to end a week ago.