The original SQL Server was 2000. At some point it was upgraded to 2008R2. I just did some extra testing and I can see the newer users have the permission access problem and the older users do not.This wasn't noticed before because the users did not need this information and most of them are disabled by now anyway.
I don't remember when the server was upgraded but I think some users without the problem were created already on the 2008R2 version.
I understand there might be a  'proper way' to  solve this  issue but it will require extensive changes because the UDF mentioned before is used ALL OVER the database. I just think there should be a way to change some value in one of the system tables to let it work. The question is which table...