preparation failure are usually due to congestion. Check out the preparation failure rate in the target cell (seen as incoming ho preparation failure) : when you look at the incoming failure, you can see whether the cause is congestion or BSS failures.
If the target cell has poor incoming HO prep failure due to congestion, it means the serving cell is having poor preparation failure due to congestion in the target cell. It’s reverse analysis 🙂
Best regards,
Pix