Wear it most of the time. Bought it new and is under warranty. About 18 months old. Regularly set it to the atomic clock. Consistently ran 4 seconds a day slow up until now. Recently after resetting it to the atomic clock it was 6 seconds slow after a few days. After a week it’s 8 seconds/day slow.

Should I try demagnetizing it? If yes, which demagnetizer to buy, or is it best to take it to a reputable watch repair? Watch seller is not local.