Mixed OSX with SMB- Now monterey - Read only issues

Hi, i am a technician in UK. (I may put this on other forms to)

I have a customer who has been dogged by "read only" issues on SMB shares.

Network =

10 iMacs (not AD joined, just "connect to server")

1 x Windows Server 2016 SMB share

Users work as "standard users" and dont have admin to their local machines.

History =

It started back in MacOS Sierra

Highlight issue was this > https://forum.vectorworks.net/index.php?/topic/56405-read-only-vwx-files-on-windows-server/

After Much invetigation

(wireshark, trying afp, disable smb 1 etc, changing permissions) we found the fix (as suggested by vectorworks support) was that all the Mac machine on the network had to be all the exact same macos version. (we standardized on MacOS Hi-Sierra) then a majority of issues went - network was then very usable

Roll on 3 years ago =

We upgraded all machines to "Catalina" did it in one weekend

Sophos Antivirus put on all machines

No other changes to the network - All good all network issues were resolved.

Last year -

Upgraded customers main application "Vector works" from 2018 to 2021 - all good no issues

This last month & now =

Weve put some new machines into the network and started upgrading existing machines to Monterey

So we have a mixture of MACOS on the machines (Big Sur, Catalina & Monterey)

No server changes have been made (other than usual windows updates)

All machines built from fresh, minimal apps installed - so we are sure only variation is different OS On the network.

So now we are absolutely dogged with "file is read only" when opening many varied files on the network. Even machines that have been untouched for years (with Catalina on ) now get the error.

So My Question >>

Is there any truth / ground in my conclusion that this issue is when different macos is on a network.

Can i expect this all to be resolved when i put Monterey on all the machines

Any other ideas?

I would love to see some really in depth trouble shooting guide for MACOSX & SMB with expected pcaps, advanced debugging etc etc.. (I have megular SMB / MAC issues with other customers as i travel)

I can provide more information - I have screen shots & pcaps of this issue thats been running 5 - 6 years. Has been googled to death.