A previous Diamond I had was having a couple of issues and one of them was that I could not get my Diamond to syn regularly.
It synced once and after that it didn't sync anymore.
I exchanged my Diamond and the replacement syncs every time
The replacement Diamond has the new stock ROM and Radio.
The ROM upgrade may be the solution. I never found out why my Diamond was having Sync issues but the older ROM had a few issues including always freezing and having to reset it ten times a day.