it happens on only one cell ? the other cells also have the same “BCCH (PGSM) / TCH (EGSM)” configuration type ?
is there TCH congestion % ?
i don’t have any idea… could you check that the EGSM TRX are taking trafic ? what about the BCCH TRX ? Is it over-utilized ?
Are you certain that SDCCH Congestion is linked to the frequency configuration of your cell ? Maybe the BCCH is just cleaner than before, and manages to take further away traffic ?