so you are 100% sure, it is a file open issue and not a network issue?
have you searched the forum?
not sure about linux, but on windows, we have https://en.wikipedia.org/wiki/Shadow_Copy
"A snapshot is a read-only point-in-time copy of the volume. Snapshots allow the creation of consistent backups of a volume, ensuring that the contents do not change and are not while the backup is being made."