EFR and AMR voice calls

Dear list, FR calls between mobile phones are working fine, but when I change the codec-list to "codec-list fr2 fr1 fr3" or "codec-list fr3 fr1 fr2", I am getting a Remote Transcoder Failure: lchan(0-0-1-TCH_F-0)[0x630d01c78b80]{ESTABLISHED}: (type=TCH_F) CONNECTION FAIL (cause=Remote Transcoder Failure [ 28 ]) In the BSC config: codec-support fr efr amr codec-list fr2 fr1 fr3 In the MSC config: mncc-int default-codec tch-f fr default-codec tch-h hr Both the phones and the BTS is FR/EFR/AMR capable. I am fairly sure with Osmo-NITB at least EFR was working with these phones and BTS some years ago. If needed, I can provide a pcap. If someone has an idea, please let me know. Regards, Csaba