I have a Seiko 6139-6005.
When I stop the sweep second hand, the watch stops running. The watch will only run when the sweep second hand is active.
I have (2) 6139-6005 & (2) 6139-6012.
I haven't worn the watches consistently in several months. The last time I wore the watch in question was 2 months ago and it was running properly. It has a 6139B movement. It was sitting on my shelf. No drops or anything.
I went to wear it yesterday and noticed the issue.
The other 3 watches run without issue.
Any suggestions are welcomed.