Here's one for the watchmakers and wannabe's - Have you ever seen this?

Ok. A friend of mine has an older Tag Heuer 2000 Professional (1989 quartz ETA) that was gaining time after a battery replacement. He shipped it to me to take a look and it kept perfect time on my desk. (???) Skeptical, I wore it for a day and noticed it was running at about twice the rate. Shock? Dirty? Took it off and set it on my desk again and after several minutes, it went back to keeping time. Can an increase in temperature cause the problem? Evidently. I hung it over my desk light (LED) which is slightly warm like an arm. Sure enough, started racing again. I did a quick circuit swap and now works perfect.

This is a first for me. Has anyone else seen this?? 😵‍💫

Twice the rate? No, not seen anything like that. Makes me wonder if something in the circuit was expanding and causing some sort of "short" that was increasing the rate, so different than the normal rate variance with temperature.

It was almost run away mode. I didn't actually time it but approximately twice the rate.
When you figure that the case temp is high 70's (F) on the table and mid 90's on the wrist, it shouldn't be that big of a swing to impact anything but it did.
If I was smarter, I would have heated the IC and crystal inside to see if one or the other was the culprit. Instead, I just swapped out the circuit and chunked the old one in the trash. No visual stress seen on the board. All looked pristine.
Been on my arm now for over 12hrs (yes, I slept with it) and still dead nuts on time.
Go figure.. 😵‍💫