ok, i was a bit blur this morning :)) what you see is actually a high rate of HO due to Quality, and on top of that, you also see a low HO success rate. Those are 2 different things, that can be related or not (they probably are, though).
In order to check RxQual in your cell, you should have a look to the RMS graphs (RxQual per Timing Advance, per Rxlev, etc.). You could activate MAFA measurements also, or simply do some drive tests.
That would ensure that it is indeed a frequency problem. Next step is to find which cell is interfering, and which frequency particularly.
You could activate the MAFA to find a clean frequency in the cell coverage area.