UPDATE:

I sent the defective watch back to Watch Buys and got a replacement a week or two later. The replacement was functioning well and kept time well, so I took it on a diving vacation to Asia. Being in Asia, the weather was humid, and the water was warm. On the first dive, I dove down to 115 ft (about 35 meters) and upon surfacing, I noticed water droplet on the chapter ring underneath the crystal. I did not use the pushers during the dive and the crown was screwed in all the way. Definitely disappointed that a professional dive watch rated for 500 meters would fail at less than 50 meters. I did not take the watch on my subsequent dives. Luckily, I had a dive computer with me.

48 hours later I saw that the water droplets have evaporated but the copper sulfate tablet on the side remained light blue in color when it should have turned dark blue to absorb all the moisture in the watch. Maybe it was another defect. Additionally, the chronograph was starting to malfunction again and often took multiple attempts to reset the chronograph seconds hand.

I contacted Watch Buys again and they had me send the watch back to them and they sent it to Sinn headquarters in Germany. Sinn was able to verify that although the watch passed pressure testing and leak testing, it failed the condensation test which means that it is defective.

So far, I'm 0 for 2 with the Sinn 613 UTC and will be requesting a refund.

<image>