I am having the same problem for quite a while.
We have a SMB share Mac/PC, CatDV server is in PC and everything works great between pcs clients. In Macs, server connection fails all the time and these STALE SESSION ERROR occur after two minutes of connection. IPs are static and so on.
The issue that triggers our Mac problem ain’t probably the same as yours but just in case, I leave this posted here. Also, we are a big organization so there might be some common traces with yours 🙂
Always good to share knowledge!
Regards