Cant see users of few groups

have tons of group folders with different users , in few of them i have problem

Schema Group1 Folder1 - Users in Group1 can see Folder1 - got 10 users there
In Users Admin Panel, when I click on Group1 it shows empty - no users inside - but whe i give in search field name of the user it will be shown …
In User List i can assign groups, Users see group1 an it works … But Administrator of that group see only empty list …Global administrator same issue …

ANy ideas ?