Section: 5.5.2.3.4 Abnormal cases in the UE
Content: The following abnormal cases can be identified: a) Transmission failure of DEREGISTRATION ACCEPT message indication from lower layers. The de-registration procedure shall be progressed and the UE shall send the DEREGISTRATION ACCEPT message. b) DEREGISTRATION REQUEST, other 5GMM cause values than those treated in subclause 5.5.2.3.2, cases of 5GMM cause value#11, #15, #22, #72, #74, #75, #76, #77, #78, #79 and #93 that are considered as abnormal cases according to subclause 5.5.2.3.2 or no 5GMM cause IE is included, and the De-registration type IE indicates "re-registration not required". The UE shall delete TAI list, last visited registered TAI and list of equivalent PLMNs (if any) or list of equivalent SNPNs (if any), shall set the 5GS update status to 5U2 NOT UPDATED and shall start timer T3502. If the UE is not registering or has not registered to the same PLMN over both 3GPP access and non-3GPP access, the UE shall additionally delete 5G-GUTI and ngKSI. A UE not supporting S1 mode may enter the state 5GMM-DEREGISTERED.PLMN-SEARCH in order to perform a PLMN selection or SNPN selection according to 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5]; otherwise the UE shall enter the state 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION. If the de-registration request is for 3GPP access only or for both 3GPP access and non-3GPP access and the UE is operating in the single-registration mode, the UE shall: - enter the state 5GMM-DEREGISTERED and attempt to select E-UTRAN radio access technology and proceed with the appropriate EMM specific procedures. In this case, the UE may disable the N1 mode capability (see subclause 4.9); or - enter the state 5GMM-DEREGISTERED.PLMN-SEARCH in order to perform a PLMN selection according to 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5]. If the message was received via 3GPP access and the UE is operating in the single-registration mode, the UE shall set the EPS update status to EU2 NOT UPDATED, enter the state EMM-DEREGISTERED and shall delete the EMM parameters 4G-GUTI, last visited registered TAI, TAI list and eKSI.