I have a Sinn 104 with a Sellita movement. I love the watch. It keeps excellent time, typically near perfect on my wrist and gaining 2-3 seconds overnight when left dial up. I read that habitual hand winding of many automatic movements can damage parts of the winding system over time. So I have got in the routine of simply holding the watch and rotating my wrist back and forth for a minute or so to move the rotor in both directions and wind up the mainspring before strapping on the watch. Oddly, in the short time it takes to do this, the watch will gain about 5 seconds. Then it will settle down to near perfect accuracy (but now at +5) when I stop winding it in this manner. Seems strange to gain a full 5 seconds in such a short time. Anybody have an explanation for this?