Group access problem

Authentication method : Workgroup (internal LDAP)
User: alex
Default group : Users
Additional group: dit
"alex" is a member of "Users" and "dit"
Two shares: PUBLIC and IT
PUBLIC has group access only for "Users"
IT - has group access only for "dit"

I`m trying to access to this shares as "alex". I open "PUBLIC" , and can`t enter to IT.
When I put for defalt group "dit" to alex - the opposite is true.
Question: Why alex has not access to both shares? without change default group ?

I`v solved this problem.
Problem appeared after an unsuccessful attempt to use Windows ADS authentification.
When I return to local LDAP, group access is not correctly work.

Just roll back to old settings help. Is there some other way?