So my brand new 103 arrived yesterday. Since it had stopped, I manually wound it - about 30 turns. Started normally, I set the date and time and wore it for 5 to 6 hours. Woke up this morning, it had gained nearly half an hour. Initially I thought I must not have set it correctly, so tested it, but realized that after 5 minutes, it had already gained 15 seconds. Measured a couple more times over 30 minutes and 60 minutes, consistently got the same average gain.
I of course called Sinn strait away - they were quite shocked and guaranteed that they test the watch multiple times for accuracy before it leaves their workshop. The lady said the only thing she could think of is that it got magnetized as it was sent via plane. She said I was welcome to send it back under warranty - they would pay for shipping, but the same thing might happen to it on the way back as all packages that go on a plane go through a large electromagnetic detector (her words not mine). She suggested I go to my local watch guy instead and get it demagnetized.
So I took it to the local place. He recommended not wearing it until it stops. When it stops, winding it up fully hence "rebooting" it. Then measuring it again. I feel like a huge gain like that is not just going to fix itself? If that doesn't work, he wants to take it apart to demagnetize the individual parts. While they are a reputable company, they didn't seem to know what I was talking about when I asked them if they would refill with Argon. Also reluctant to had it over a day after receiving it.