Symptom:
Customer recently noticed some issue with using CLI card busy-out on the MME

When the card busy out is enabled on a certain PSC card in the MME, the expected behaviour is that no new calls  (IMSI  attaches) attach to  this card and the existing users upon detach (GUTI based attaches), would reattach to another card in the same MME. However during lab testing it was noticed that  when existing users on that  upon detach (GUTI based attaches) and reattach, are unable to get service in LTE, as the MME does not assign them to another session manager. 
This causes loss of service for the subscriber until they are purged from the chassis.
Detailed description in the enclosure

Conditions:
When Card Busy-out CLI is given on any PSC card on MME