My nine month old Seiko 5 with the 7S26 movement started gaining about 6 minutes per day when it was six months old. It happened rather suddenly at the six month mark and has remained that way the last 3 months (hasn't improved or worsened). I have included Timegrapher results below from when the watch was new and now.
Is it possible it has become magnetized or is it more likely to be a mechanical problem? I have a demagnetizer but haven't tried it on this watch, yet. Do I have to remove