Some time ago it would only scan for about 30 seconds and then say “completed” (even full scans). I thought I’d handled it but it started up again. I do a boot scan and that works normally and says no infected files but then it refuses to scan right once booted up, and sometimes the Avast just shuts down or is disabled. I strongly suspect I’ve got some kind of infection but I can’t find it. Can anyone advise me, please?