If ICM is high (2-5), try to see if the affected freq are on BCCH TRX or TCH TRX.
Also, check for drop reasons.
Then, compare with the ICM readings.
It would tell if the ICM is on BCCH as it would show on the reasons as Bad Quality Downlink.
If it is on a TCH, it would show as Bad Quality Uplink.
Change the affected frequency.
record FAS to find out what clean frequencies you could use..