Accounts lock and won't unlock...

Since we have upgraded to Contao 2.11.2, we have been having many problems with users passwords seeming to mysteriously change and we are unable to login, today we looked in the database and the accounts that we have been having problems with seem to have information in their login, which shouldn't be there... In the login column it should be 0, but there are numbers in there, even if we change the password in the backend or if a user changes their password... Is this a bug? Or is there something wrong with our database? It seems as if the user sometimes can login after we change the password, but sometimes right after we change the password, we can't get in...