Hi, So, I migrated to today's master, and tried with MNCC local to make sure the PBX is not participating. Using an E1 based Nokia InSite and the target codec is EFR (as the InSite does not support AMR). And the test case is a MO - MT call. On the BSC config: codec-support fr efr codec-list fr2 On the MSC config: mncc-int default-codec tch-f efr default-codec tch-h hr The BSC log say: Tue Jul 25 21:53:45 2023 DCHAN abis_rsl.c:1291 lchan(0-0-2-TCH_F-0)[0x562876541b90]{ESTABLISHED}: (type=TCH_F) CONNECTION FAIL (cause=Remote Transcoder Failure [ 28 ]) Tue Jul 25 21:53:45 2023 DMSC osmo_bsc_bssap.c:1465 SUBSCR_CONN(msc0-conn1_subscr-IMSI-001010101000050-TMSI-0x910bc287)[0x562876543a00]{WAIT_CLEAR_CMD}: Event MT_DTAP not permitted The MSC log say: Jul 25 21:56:46 openbsc osmo-msc[759]: <0001> transaction.c:130 LCLS disabled globally Jul 25 21:56:47 openbsc osmo-msc[759]: <0007> mncc_builtin.c:373 (call 80000007) Message 'MNCC_RTP_CREATE' unhandled Jul 25 21:56:47 openbsc osmo-msc[759]: <0001> transaction.c:130 LCLS disabled globally Jul 25 21:56:48 openbsc osmo-msc[759]: <0007> mncc_builtin.c:373 (call 7) Message 'MNCC_RTP_CREATE' unhandled So this seems to be an issue within the Osmocom stack, the external MNCC connection was disabled. Regards, Csaba