Problem: UMC settings appear to be correct but users do not have proper access to shares
You have configured a share and set alls permissions in UMC correctly as shown:
Even advances Samba options are fine:
But still some of your users do not get access to files even though you have verified the ACL settings in Windows.
Solution
ACLs in Windows might lead to confusion sometimes due to their inheritance. You should remove all ACLs from the share and configure the ACLs from scratch on Windows.
To remove all ACLs, so:
setfacl -bn /path/to/share