In case, that you have same combination BCCH/BSIC on two sector neat to each other, on the some other (at least one) sector there will be a lot of HO failure.
For example: you have sector A and B with same BCCH/BSIC combination. This two sector are not neighbouring sectors. You have sector C. Sector C is in the direction to the sectors A and B.
On sector C is defined HO to the sector A, but not defined HO to sector B. Mobile is served by cell B. On the border between cell B and C mobile measure and report BCCH/BSIC of the cell A (which is defined as a neighbour).
In the statistic there is a lot of HO failure from cell C to the A.