I had issues getting mine to sync up until someone taught me the "trick" (skin to skin contact). Once synced, I have never had a failure in about 300 dives. I have also never changed the transmitter battery in that time.
Can someone enlighten me to the 'skin to skin' contact trick? I am typically very careful with the syncing procedure after I realized how sensitive the Vyper Air is. The last couple dives the transmitter has failed each time for a few minutes at a time. On the last dive it failed after 30-40 min and never re-connected. I haven't changed the code since initial set up, but always get within a short distance of the transmitter, turn the computer to Dive mode and turn on the air - initial air pressure reading and go.
I think I am going to replace the batteries just to be safe, but dealing with the transmitter failure is annoying.