I also have a Patek Philippe Aquanaut 5167A . It was purchased from my local AD about six months ago. It’s a great watch that I thoroughly enjoy and it gets a lot of wrist time. The problem that I am having with my Aquanaut is that it stops dead if I put it down for about 18 hours .It is supposed to have a power reserve of 35 to 45 hours, but it does not come anywhere near that kind of longevity. And so.... like you, I will be sending my wonderful Patek Philippe Aquanaut in for servicing. Fortunately it is still well under warranty. The situation is really a heartbreaker. I have been purchasing Patek Philippe watches for more than 20 years ( and will continue to do so). I am a serious fan of the brand and truly enjoy what they are bringing to the world of watches. Back to wearing my 5320g Perpetual Calendar every day. Tough ol’ life!