The Ikelite DS-51 strobe intereferes with the Luna, I had to make sure the strobe was on the opposite side of my housing from the wrist I wore the Luna on. As other's have said also make sure that the Luna and transmitter are on the same side of your body. You can clearly see this by turning off the strobe and then sit and breath, you'll see the pressure drop, then turn on the strobe and the pressure will freeze and ultimately error out.
The DS-160/161 will do it if you hold the strobe in contact with the case, the Sea Dragon lights from Sealife will do it if they are close, and the Underwater Kinetics dive lights also do the same thing. Once you know the issue it's pretty easy to hold things in the other hand or replace them, but it's worth knowing it can happen.