I saw 2 instances of the Nauticam 9" dome port popping off, both times in the last 4 weeks from 2 different domes, all of which were bought in the last 5 mths in South Africa. They happened on land without huge pressure changes but a bit of jolting from the surf launches. The first one happened when it was sitting in the car. Apparently the SA local dealer says the O-ring used were a bit thin, so there's a thicker o-ring kit that supposedly fixes this issue.
Since these were relatively new domes, I'm assuming that this issue is from the manufacturing side of things? Or is this just an issue with old stock being sold without the updated o-rings.
The 2 guys who suffered this problem could've suffered catastrophic floods if they didn't check that the port was still intact on the plate assembly (not something one would need to check for!). One guy was so fearful, only having one body, that he started handing his camera up dome up etc. He'd asked for the O-rings to be sent out on location but they never arrived after 12 days. It never did fall off again.
The same issue was mentioned by another member in this thread: