GMT Master II going nuts

[stanima]

I just got my GMT Master II (16713) back from servicing.

When I first started wearing it I was overjoyed with the improvement in accuracy, it went from +40 -100 seconds a day to + 5 seconds in 3 days (1.66 seconds per day).

HOWEVER, on the 6th day it jumped 12 seconds.The next day +10 seconds. Yesterday it was +21 seconds.

I am just really confused. The mainspring and axle were replaced, plus gaskets etc. The watch should not have become magnetized or anything (presuming the new mainspring is the type that won't get magnetized) as I don't work around strong magnets. I do use a laptop for work, but the speakers are up by the hinge, not under the wrist-rests.

I will be contacting the person who performed the service on Monday, but I was wondering if anyone had any ideas. Could it be something like the lubricants taking a week to be properly distributed and now the timing has changed from when it was regulated?

Thanks...