Sticky multi-selector button...

I used to build my own housings, and never had a housing serviced (except by me) even when I had Seacam and now Nauticam. My D800 housing developed a sticky multi-selector button so I thought I would service those controls... If you want to know why housings seem expensive, have a look at the link for the patent for the Nauticam multi-selector. https://patentimages.storage.googleapis.com/4c/16/6b/726d94445d785f/US8787745.pdf

As Alex Mustard once said, "Deeply impressive engineering." Extraordinary time and effort  must have gone into creating something we take for granted. So unless someone has made a video of disassembling this, I think a spray of silicone oil will have to suffice, for now...

It is funny they have patented the multi selector, it looks super complicated and I doubt anyone copying it.
However, it works great on my D500.
Let me know how it goes with the silicone grease, the play / F2 lever in my housing is also sticky.

Thank you for posting the Nauticam housing patent, it is hair raising to read, next to impossible to visualize and understand how the control levers are designed.

I had a Nauticam NA D500 housing for my Nikon D500 camera, it worked just fine, never a problem for the 18 months I owned it.
But as I like to service my own housings, and as I looked and looked at the levers in my housing, I realized it would be foolish for me to try to clean and service it when the time came, so I sold it while it was still working perfectly. 

 I replaced it with a Subal housing, which like my other two Subals, is simple yet of elegant design, with all the controls accessible and easy to remove, clean and when needed, replace.  Today I have serviced my Subal ND7100 housing, an easy and rewarding experience.

Silicone spray and working the controls seems to have freed things up. I should emphasise; NOT WD-40.