Samba server 4.16 - file transfer really slow

Hello, I have a small home file server running Samba which serves 3 Windows 10 clients. Everything fine until about 2 weeks ago, but now there is often a delay of around 10-20 seconds when opening a file stored on the server. Browsing (using Windows Explorer) seems to be fine. From /var/log/samba/log.smbd I have

smbd version 4.16.0-git.227.931848a12abSUSE-oS15.9-x86_64

and the log file includes something similar to this entry against each of the affected files:

  fsp_get_io_fd: fsp *...share-path-to-file...*] is a path referencing fsp
[2022/04/24 10:12:35.704497,  0] ../../source3/smbd/fd_handle.c:118(fsp_get_io_fd)

Does this mean anything to anyone?
Thanks for any pointers

Does this happen with Linux clients as well?

On the Windows (client) side, these might be worth reviewing first…

A wireshark capture may be required to get a better understanding of what is occurring here…

It seems not. In fact it only appears to affect certain Windows applications - so far MS Office 2007 and Acrobat DC Reader. Opening even large text files in Notepad is instantaneous, as it was before. The Office suite hasn’t been updated in years, obviously (though the Acrobat is latest version).

I’ll have a look at the wireshark capture, though I’m a bit out of my depth. Thanks for the suggestions.

If you install the latest version of LibreOffice on one of your WinX machine, how does that fair?

Good suggestion. Done that, and after trying a couple I have the same problem with the same files. So I think I need to try and narrow it down and find exactly which files are affected and what they have in common

Check that file validation is not at play here perhaps…

In Tumbleweed, is it possible to temporarily downgrade Samba back to v4.15 to check whether that is the cause? To do that, do I need to roll back the whole system to an earlier snapshot?