the first strongest neig. BCCH is 6 (-70 dBm) and the serving is 5 (-89 dBm). So, adjacent channels, you were already interfered. Can’t HO to second neig. with BCCH 14 (-78 dBm) wich is again interfered by forth neig. adj channel with BCCH 13 (-84 dBm). I think you should do frequency re planning in the area. I agree with Pix, first check the indicators Pix mentioned adding the DL_Quality_HO, UL_Quality_HO, RMS Voice Quality due to Interference.