I have been using Nauticam housings since 2012, and my current one (A7II) since 2016. Two weeks ago I was doing some photography in an old mine. On the first dive I had no problems, but on the second one (i did not open the housing in between) the leak sensor was going red after 20 minutes, 37 meter down and soon I could see the water filling up the dome port. I kept the dome port downwards and the canon 8-15 lens was partly under water. The lens was fine, but unfortunately the camera display was dead.
The only thing that was new is an extension ring to fit the canon lens (instead of my Sigma 15 that I used before), but I did an 40 meter 80 minute dive with this setup some days before without any problems.
Afterwards I checked all O-rings, cleaned and used greased before checking vacuum for 24 hours before the next dive with my spare camera. However the exact same scenario happened. After about 20 minutes at 32 meters the alarm went off again, but this time i called the dive more quickly and could save the camera and lens.
Does anyone have a clue whats going on here? It's really hard to find out when the vacuum check is all OK before diving.