I had a very similar problem. In addition, I found the error 0x80508014 appearing in Windows' Event Viewer (see Review event logs and error codes to troubleshoot issues with Windows Defender Antivirus). Joanne's answer in the thread Where to restore quarantined items in Windows 10 creator update? solved the problem for me:
- Open an elevated command prompt (open start menu, type cmd, right click, choose "Run as administrator").
- Navigate to C:\Program Files\Windows Defender ("cd C:\Program Files\Windows Defender" [Enter]).
- Run "MpCmdRun.exe -?" to see a list of available commands.
- Use MpCmdRun.exe to recover the quarantined files to a different location. I created an empty folder named "DefenderRecovery" in C:\ and then ran the command "MpCmdRun.exe -Restore -All -Path C:\DefenderRecovery".
Before the recovery, I also (temporarily) disabled Windows Defender's real-time monitoring.
Hope this helps.