in such cases, even though you have already performed the verifications, it’s still probably a problem in MSC B.
If there is no initial HO requests, check that target cell is well defined in the serving OMCR.
If there is a “external” HO request from the serving BSC (from MSC B), but there is no HO execution (no ho command), then it means the MSC B is “stopping” the HO from hapening. Perhaps because it can’t find the target MSC, or the target cell.
IMO, you should check again the MSC B…