in your current software release, is it possible to use TFO with AMR?
In some releases, if the call is AMR, TFO is automatically disabled. Both features are not compatible.
If TFO and AMR can work together, then it starts to be too complicated… You could first check that both TC’s and both cells are using the same parameters ?(codec sets, thresholds, etc)
If that’s the case (for ex, both OC and TC in the same cell), then you could investigate by doing a call trace : is the UL codec of the OC the same as the DL codec for the TC ?
(oc : originated call, tc : terminated call)
And vice-versa : DL OC is same codec as UL TC ?
If you see a discrepancy, then TFO and AMR are not properly coded in this software release. Based on your measurements, you should be able to discuss with your vendor…