Well, if it's repeatable (happening more than once) somebody should make a bug report post. Maybe HTC will respond and let you know if it was something that got changed, or just your latency affecting it.
If you've got film of said experience (bullets hitting, no damage, later got an assist) post that, as they can pick the film apart far more than you can, and tell exactly how many bullets hit and how much damage was done, possibly indicating where the problem might be.