Troubleshooting some Drupal and CiviCRM accounts becoming mis-linked
The second part (tons of contacts with just the email address) is "normal", it's when civi realises that it doesn't have a contact mapping the drupal user and tries to create is with the limited info it has.

As for the first one, it isn't something I've experienced. Do you have a standard drupal for the accounts or are you using extra modules related to the account managements (eg. LDAP integration)?