1. If the problem is interference, kindly check DL interference per TRX (perform drivetest),check UL interference (on idle TCH per interference band on statistic counters), check handover attempt distribution (if high attempt due to quality -> interference)
2. If the problem is DL/UL power, kindly check HO attempt distribution (HO due to UL/DL Level should high)->check the feeder connection,maybe cross feeder,check combiner connection and check TRX
3. Kindly test with this, swap all TRX in to other cells, if the problem change to other cell->the problem is on the Module
Goodluck