i wuold think that in some cells, there are MS which are not EGSM compatible. I’m surprised the models you are listing are not… they should be…?
Could you try to do a kind of SFH with one MA-list containing only the P-GSM band frequencies (all TRX that carry BCCH and SDCCH should be in that band) and another list with the extended frequencies only.
Then you should set a parameter called “RR ALLOCATION EGSM” (or something named like this, I can’t remember the exact name) to the value meaning that PGSM MS should be handled differently than EGSM MS.
If you try that and it works, it means indeed that the TCH failures are coming from non EGSM phones.
Also there is an indicator that counts how many phones are EGSM compatible in your network. I forgot the name, but I’m sure you’ll find it. It’s probably a cell indicator.