Ok, I'm regretfully posting this.
Back in August, I sent by Lunova Tag/Datum to be serviced under guarantee by Mühle due to it not keeping the power reserve. I personally picked it up in Glashütte back in August, when I asked why it was not keeping time, they told me that it must have received a shock (had been dropped) at some point. Personally, I have never, ever dropped, hit or banged the watch (I love it, so I baby it), so I can only imagine it had previously happened at the AD or in transit to the AD.
It was running perfectly since then. I do not wear it every day, only on special occasions, or when I feel like it. Meaning it can be for days at a time either on my wrist, or in storage.
Yesterday afternoon I synced it to www.time.is (it was 1/2 a second behind when I synced it), and wore it for a few hours, but took it off in the evening.
It was still running at 17:00 today, so I put it on. When I checked the time at 21:38 compared to time.is, it was more than 30 seconds slow. It had been laying flat on a desk overnight / during the day today.
Before I ask Mühle to take another look at it, I wanted to ask you guys if this could be from a lack of power reserve on the main spring (ie: it was not fully wound)?
Has anyone noticed that a Sellita SW 220-1 runs slow when not kept fully wound?
Or might it be that this movement needs an adjustment again after only 6 months? I can't believe that it would, unless there is something wrong with the movement itself. I am loath to send it to Mühle again as it is expensive to send.
Thanks for your input.