Hi Alex,
VFP 8 and 9 both predate mysterious intermittent access/concurrency issues associated with Windows 10 and later.
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.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
