interesting as my cal 12 1153 i recently acquired has the exact same problem. except the chrono will run until 15 minutes and then stop. i'm thinking my problem is that the 12 hour wheel is engaging right around then, and it was serviced recently, but not by Hans. my theory is the watchmaker maybe assembled it wrong or maybe missed something when putting together the chrono module?

i'm taking mine to my local watchmaker who happens to like heuers and talked my ear off about cal 11 and 12, when i mentioned the term microrotor once. even has a dashboard piece on his desk. he's not Hans, but he is probably the next best locally. check around you may have a watchmaker like mine nearby, if not there's always lvmh after sales service (protime). btw i thought that mine was a winding problem initially also, but after a few days of wear and it was keeping near perfect time, i'm convinced the chrono module is the problem.

j.h.