I'm fairly new to mechanical/automatic watches, my first is a Seiko Alpinist (SARB017) and I noticed my watch had started running several minutes fast each day. I never dropped it or anything, and it's only about 6 months old, so the store I bought it from replaced it.
I just got my replacement in the mail at work today and set the time, checking it every couple hours to see if it was accurate. While I was at work (maybe 5 hours) it only gained a second or two; however, about halfway home on the DC metro (I'm on the train for about 45 minutes) I checked and the watch was already a minute and a half fast.
Is it possible riding the train could be making my watch run fast? I believe the SARB017 is anti-magnetic, so I would think that wouldn't be a factor.