New to watches, I would venture a guess. Since it was behaving as expected for a full 8 days, then started to switch the date incorrectly, would imply something broke, or became misaligned, or loose at day 8.
Obviously I haven’t a clue, but it’s fun to speculate!
would appreciate and update when you figure it out.
A gold plated champagne dialed "Kudu" joins the club.
This 17 jewel Swiss front loader needed a service, a crown and stem to get it running.
It also benefited from a complete valet, and a crystal polishing session.
Finding and fitting a suitable stem was the most tricky part, since the original had broken off right at the edge of the base plate, so extracting without stripping it down was a non starter, and finding something to match the broken stub in my "pile of random stems" took a fair bit of scratching around and experimenting.
It looks a whole lot nicer in real life than it does in my rather badly lit photograph.
The strap was borrowed from an HMT Kohinoor which is hopefully going to be the next patient up on the healing bench.