Sub 41 Accuracy Question

[prk154]

I've had my new sub for about a month now. I set it immediately based on the atomic clock and have worn it every day since. For the first couple weeks, it consistently lost about one second per day...which is great by my standards.

The interesting thing is that it has been gaining back time for the last two weeks...to the point where it is almost back to being dead-on accurate with the atomic clock.

Is it normal for a watch to lose and then reverse to begin gaining time...or vice versa? I was always under the impression that it would only move in one direction.