GMT losing time on a winder

[PRH]

I know there are split opinions of whether or not to use a winder, so I do not want to get into that discussion.

I got a new Rapport Winder last week. One that has an alternating rocking motion. It probably turns the watch through a little less than 45 degrees each rock rather than full rotations. So each full movement is a little under 90 degrees.

I have noticed that both my GMTII and Sub, start to lose a few seconds a day when on the winder but on my wrist they are within +1 second a day.

Has anyone found this scenario?

I do wonder if the winder is not winding the watch sufficiently.

It rocks for 1 minute every 15 minutes.

Any comments would be much appreciated.