Weird thing happened to my high accuracy quartz movement. It seemingly ran -20s in 1.5 days. Which I suspected might be due to me setting it incorrectly when going into winter-time. But then it continued to loose another 2 seconds over 8 hours the following night, just laying on a table. Yet, after that it has somehow reverted to again run perfectly, at +0.0s per day like a HAQ movement should do.

Could it have been magnetized, and then gradually de-magnetized itself?

I can’t really think of anything that makes sense to me, that could have caused this weird behaviour.