FFS causing application programs & Windows 10 to hang

[Alan1951]

Previous versions of FFS backed up open files by (rather slowly) creating shadow copies.

With a very large PST file, the latest version gives me the following error message:
Cannot read file "F:\Documents\Archived E-mails\Archive.pst".
The file is locked by another process:
Microsoft Outlook, "C:\Program Files (x86)\Microsoft Office\root\Office16\OUTLOOK.EXE"

If I quit MS Outlook and select Retry, copying of this file proceeds for a while but then FFS stops responding. Task Manager shows that FreeFileSync_x64.exe is not responding and neither it nor FreeFileSync.exe are using any CPU.

I can quit web browsers but, if I try to interact with Adobe Reader or MS Office applications, they also stop responding. When I try to restart Windows 10, the machine hangs on Restarting...

Any ideas?