there is HO failures from 900 to 1800 cells ?
or also from 1800 to 1800 cells ?
There are also a lot of HO from 1800 to 900 due to bad quality ?
From 900 to 1800, please provide values for those indicators:
Does it happen on 1 cell, few cells, or many cells ?
Most common cause for outgoing HO failures is poor radio conditions (bad rxlev or bad rxqual).
It is further confirmed by the high amount of HO QUAL measured in 1800 cells.
It proves that 1800 frequencies are quite interfered or provide a low coverage, which result in:
1/ hard to keep HO from 900 to 1800
2/ happy to trigger HO from 1800 to 900 due to bad quality.