you could try to isolate which 2G target cells are bad.
you have 2 main scenarios :
(1) for some cells the HO SR% is 0, and for the others, it is better than 95%…
–> what is the problem in those target cells ? specific BSC ? wrong 2G external info (bcch, ncc, bcc..?), wrong BSC info, wrong LAC..?
(2) all cells are bad, with a HOSR = 50% -> you should investigate at the RNC-MSC level
Once you have isolated the bad cells, it would be really convenient if you could do a IuCS trace.