Re: Cannot reproduce the net share issue...
I rather suspect that Microsoft is mucking around in SMB again, probably in an attempt to rearchitect/reengineer it yet again.
I believe the issues with SMB mounts not reconnecting is due to activating the Hardened UNC Paths feature by default. So it's not "mucking around in SMB" in the sense of altering the protocol itself, but in adding security features to their SMB client implementation (which it desperately needs, of course) which break some existing connections. But I admit that's a subtle distinction.
The October update broke Group Policy Updates to my corporate laptop, for example, because of an authentication failure. (I didn't bother investigating further to figure out which machine was failing to authenticate the other.) I had to configure HUP in Group Policy (on the client) to not require mutual authentication for SYSVOL shares to get it to work.
There are various articles online discussing the issue.