The first solution can be given by antenna engineering. If the traffic is comming from far away then you need to enhance the coverage. Go for TMA.
Sometimes the failure in intra handover is caused due to deffect in Carrier Unit. The status of Carrier Unit will be OK from OMC(Radio Commander) but when we perform test the Carrier Unit then there shows the failure in CU. I have experience this case in Siemens BTS.