7 hours ago, ChrisRoss said:
Both the extension and it's o-ring are new I would assume and just because it's new doesn't rule things out - it's always possible something slipped through QC. Davide's point on a bad o-ring could be the issue - inspect that one closely and compare it to o-ring on the port. If you have a micrometer or calipers, measure the diameter (cross -section) of both of the o-rings at several points around the o-ring. Try not to mix them up - you may want to do comparison tests later.
You could for example run tests on a rope at depth with the current setup and o-rings. Then with a new spare port o-ring, then with the housing and and port without the extension. You would need to keep track of which o-ring is which to avoid confusion.
I can report a case with a new Nauticam extension/adapter (SKU # 36064): I ordered it new and after the first dive few drops of water came in via the opening of the locking mechanism. I assume the extension was lying around in the shop for long and the O-ring became dry and rigid. I solved the problem with a drop of this fluid: https://www.unterwasserkamera.at/shop/catalog/en/product_info.php?info=p6154_d-d-top-secret-o-ring-fluid.html
Every year I treat all concealed O-rings via the opings of our housings with this fluid and there was never a water entry. I can also say that some controls of the housings, that were purchased second hand, ran noticable smoother after the first treatment...
I agree that it would be better to remove the O-rings and grease them with original Nauticam lubricant (and replace O-rings, when worn out), but so far I was reluctant to do this substantial amount of work, hopefully I will never regret this...
Regarding the problem of tobbe1, I would not risk another flooding by continuing to dive: the leakage has to be located (with paper towels as already suggested), the entire mechanism removed and the O-rings replaced. It is very likely a worn out O-ring that sometimes seals, sometimes not (unless it is a strange user error, impossible to diagnose this from remote)...
Wolfgang