By file manager I meant as a Kodi smb connection. This is a way of isolating where the issue is coming from to narrow it down. If you think this is a ridiculous idea then don’t try it.
The only other thing I can think to suggest is the same thing with a NFS system mount and see if that is more robust.
or alternatively you can try autofs which some people find works the most reliable especially if they have a less than stellar network connection.