handover failure

[radio_network]

we are facing a unique problem of handover failure from one sector to another sector in same site in more number of sites. Nortel and Motorola systems.
The statistics shows good number of success against attempts from one sector to another sector but in the reverse success is in less numbers against attempts. Any suggestions pl.

:):)

[RF engineer]

There is no interference on the cell that failure is high

[radio_network]

we are not able to fox this problem with drive. With atol it seems to good . The statistics showing this figures.