Paul,
I've tried everything I could think of, but nothing helps. I even uninstalled SAMBA from the server, deleted all files in C:\MPTN\ETC\samba (there were 55000 files in\lock\msg.lock !) then reinstalled the Netlabs package, and upgraded to your latest SAMBA but still have the slowness issue at the client. Went back to 4.11 on the server and everything works well, even the 4.18 smbclient on the client machine works without -t 60 then.
BTW, deleting those 55000 files makes the server start MUCH faster. Wonder if there is a way to clean those up before the server is shut down...
Regards,