mmm.. ok, a lot of questions :
Can you check whether the inc ho congestion occurs for intra-HO or intercell HO ?
In which cell does this occur (band, type, neighbors, coverage, multiband, concentric..? any thing particular ?)
how many HO inc requests ? how many TCH NA requests ? RTCH Duration average per TRX ? path balance average per TRX ? Erlang FR TCH per TRX ?
what is the neigbor cell that generates so many HO (check the adjacencies indicators) ? what is the main cause of HO in this neighbor cell ?