Hi @guidocasati I'm using OAI UE on latest `develop` branch, UE failed registration in SA mode with 3rd party gNB + Core Network. Network will send second NAS Security Mode Command after UE capability information. If I use version without MR !3176 , UE can finish registration. Below is command used to run UE: `sudo ./nr-uesoftmodem -O ~/uxm_ue.conf --band 3 -C 1815000000 --CO -95000000 -r 106 --numerology 0 --ssb 6 --agc --clock-source 1` Below is UE config file: [uxm_ue.conf](/uploads/d6b2ca331f4cb72681badbd9d643a787/uxm_ue.conf) Below is UE log: [oai_ue_sa_reg_fail.log](/uploads/8968c1201b367080d34384cafc30f7a0/oai_ue_sa_reg_fail.log) I'm suspecting IE `NAS key set identifier` in Registration Request message caused this issue, in ok case this value is 1, but in failed case it's 0. Could you please help take a look? Thanks!