My 857 UTC stopped working a little over five years from being purchased new at Watchbuys. This is the timeline of its service visit to the factory in Frankfurt, should anyone want a recent ETA on similar service.
Shipped via Fedex on 12/15/2018 from USA, at a cost of $127.90. This is the cheapest cost from Fedex. It arrived there on 12/18.
Sinn emailed me on 12/18/18 that it was received, and would have a processing time of 13-14 weeks, and that this ETA varies based on the amount of work needed.
Sinn mailed a letter to my home on 01/16/19 confirming the cost, and this is usually when you the customer choose whether to have the work done or not. When I sent the watch in, I signed and gave them authorization to go ahead with the repairs. ETA for remaining work time: 12-14 weeks.
Sinn emailed me on 4/25/19 that the work was completed. I paid via Paypal on 4/16/19, which was a nice option that I had never done internationally before. No hassles.
Watch was received at my work on 5/13/19.
The watch came in a foam lined cardboard box. Inside the box was a nice shipping case, foamed lined. I will keep this for future travelling.
The case was sealed in a clear, plastic protection sleeve that must have been installed with the strap disassembled. It is very tight, so my guess is that it is slightly heated to shrink around the case. I had to cut it off.
Also included were the used parts. Two gears from the movement, the crown, case seal, the copper sulfate capsule, mainspring (?), and my original second hand.
Why was my second hand in there? I requested the newer, luminescent second hand from the 857 UTC VFR. I always disliked the fact that the normal 857 UTC's second hand does not glow. It was only 5.71 Euros more...
Overall, the experience was hassle free and Sinn was very quick and responsive to any inquiries I had. As long as you are patient, good things come to those that wait!