For the past couple of weeks, Windows 10 users have been reporting that Windows Defender scans are skipping files due to a configured exclusion or network scanning setting.
The users who report receiving these messages, though, do not have any exclusions configured in the Windows Defender preferences.
Even still, when they conduct a Quick Scan or Full Scan using Windows Defender, a Windows 10 Action Center notification will be created that states that items were skipped during the scan with the following message:
Items skipped during scan
The Windows Defender Antivirus scan skipped an item due to an exclusion or