Win 7 SP1 and Server 2008 R2 security updates for Jan 2019 breaks network shares in some instances (if the user connecting to the remote is also an Admin user on it).
Fix is to uninstall the Win update (which removes some other security updates), or there's a registry hack that may work (did for me).
Or wait for Microslop to (maybe) issue a fix.
Check ThatBigSearchEngineWeAllKnowAndLove for "KB4480970 KB4480960 network issues" to find details.
