Iv'e been scanning a multi site network of 6 sites for the past 3 hours and it still hasn't completed and is stuck on "Scanning for known malware files".
Usually if a scan goes well on one site it only takes a few minutes so I don't think it's taking longer because there are more sites.
When this issue occurs on single sites usually killing the scan and retrying a few times works eventually, but not with the MU scan.
None of the troubleshooting iv'e found online about this issue has helped.