When you perform a quick scan (manually) for a drive or custom folder with Avira free Antivirus, after completing the scan it logs detailed scan report and displays it, which is not the case with scheduled Quick System Scan set by Avira which runs once for every 7 days automatically.
When the scanning process about to complete (at 98.6%), Avira Free Antivirus throws an error dialog ‘The report file could not be created’. Seems this has been happening since March this year , but the German security vendor yet to resolve the issue.
Avira Free Antivirus: ‘The Report file could not be created’ error
One way you can avoid this error by disabling Quick System Scan for Scheduler, you can do that by
Avira Free Antivirus interface> Administration>Scheduler, remove tick mark under Enabled on right side.
Or since the scheduled quick scan happens once in a week (other wise if you’ve set it for less number of days or hours) you have to ignore that dialog until Avira fixes it.