so the synchronization is controlled by the “clock” in your BTS. In ALU, it’s called the SUM board. In Ericsson, the DUG. In other vendor, it’s usually referred to as the digital board.
Anyway, I don’t think that’s the problem.
Check your Qos Stats : What are the cause of the HO ? Quality ? Level ? Best Neighbour ?
Try to find some indicators that show details about the HO failure you’re seeing : preparation fail, execution fail, which neighbour is failing to.
Here is a gut feeling : I think you’re issue comes from configuration, either Core Network conf (wrong LAC, wrong CI, wrong whatever) or OMCR conf (I can’t think of anything… wrong Abis conf ? wrong backbone transport conf ?)
100% fail… you gotta look at a huge conf issue. HW was changed already, so that is ruled out.