Could you please share the main KPIs for that site ? (TCH drop%, HO qual%, CSSR) before and after the modification.
To improve the DL Qual in case of SFH, the strategyis to reduce the overlapping coverage between surrounding cells and this cell.
Therefore, try downtilting / re-azimuthing the neighbours’antennas. You can also tilt the “bad” cell, in order to reduce its coverage, as long as the coverage is still satisfying for your planning.
Other “soft” solutions : activate DL/UL power control and DL/UL DTX. If those are already activated, try enhancing the power control thresholds. Put them 3 or 4dB lower.
Reduce the HO MARGIN, so that the MS will go to the best serving cell faster. For ex: instead of HO_M = 5dB, try 3dB… but on the other hand you must increase the averaging window.
Finally, you can remove TRX’s in the bad cell and in the cells around, to reduce the radio frequency load. And activate HR, to balance the capacity loss.