>VFP 8 and 9 both predate mysterious intermittent access/concurrency issues associated with Windows 10 and later.

The SMB gremlins stay well fed unless you purge them since Vista.

My expirience with Win10 is oodles better compared to Win7 by not diconnecting (often external) discs or subst-drive letters.
I guess they still disconnect sometimes, but afterwards reconnect, which Win7 often failed to do.
Even dis- and reconnecting by just switching power off in USB Hub works well, also mapped UNC drive.

>
>I know it's a VFP8 app, but it might be worth experimenting with VFPA that automatically retries various disk interaction commands (copy etc) in case there's one of those brief OS issues. It usually defaults to 3 retries behind the scenes which appears to be enough.
>
>The other one to consider is virus scanning: if a scanner seizes something that VFP thinks is exclusively open, you can see index or other unexpected errors that disappear after a debug pause or reindex.

regards
thomas