Brand new MK2s which so far I have loved on the couple of dives I have done with it. However less than a week old and the top right button has fallen out. A little disappointed..... Anyone else have this issue?


Yup, for me an unfortunately common issue. I returned my first MK2s after the bottom left button fell off and I couldn't find the springs from the inside anymore.
On my replacement watch, the same top right button as for you gets very loose during activities/motion and has been very close to falling off a handful of times.
I try to remember to spin that button like a screw inwards throughout the days which seems to help with the issue. All other buttons on my watch are solid so it seems it's an intermittent quality issue affecting only some buttons.
Same button on my MK2s almost become loose and almost falling off. To me this is like a manufacturing defect. I send back to Garmin, is already almost 2 months, still not returning to me yet. I really disappointing with Garmin service. No sure if it is the dealer delaying or is Garmin service team.
I had the same problem twice actually. The first time I returned my watch and now it is happen again. It is very annoying because the watch is so expensive and it is the same problem. It is a manufacturing issue. I am going to contact them again. I hope you managed to sort it out!