Syed,
Bad HO are mostly due to interference, bad coverage or congestion.
Patrick,
Parameters can’t cause HO failures ! The parameters just control the preparation of the HO (what is the cause of the HO ? which cell will be the target for this HO ?). They do not prevent a HO to execute properly.
On the other hand, you can prevent a HO to be detected : by not defining a neighbor relationship, or by putting a very high HO MARGIN, or a very low L_RXLEV_DL_H, etc…
Regards,