I have a domain joined Windows 10 Enterprise (upgraded from Win 8.1) with a local user "x". I create a share and give "x" some rights on the share, Read or whatever. Folder rights are covered by "Everyone" but I can also give "x" explicit access, doesn't matter.
Now I do
net use \\mycomputer\share password /user:mycomputer\x
This works fine on my local machine and on two other Windows 10 computers, but not from a variety of Windows 8.1 machines (including freshly installed ones). The error shown is "Access denied".
When I look at the Windows security event log on the share machine I see a successful authentication for user "x", followed by a logon for that user and (only in case of "access denied") an immediate logoff.