Battery curse..... yeah yeah yeah 😉 You know you are all secret closet quartz geeks
It's a contact issue, common with the 1620, take the case back off using a case back knife (press on) and give it a blast of compressed air then pop the movement out (drop in with no screws) and clean the contact with a cotton bud, usually does the trick
I've got a few of these (great watches although the build quality leaves a little to be desired)
Hope it helps, PM me if not
Tom