Some guys wind it too hard when it stops and then sometimes the mainspring broken. I just would wear it one day and it stop winding after like 10 turns. I'm not think so much about it but when it stops after 6 hours I try to wind it and it was stuck.
they change both mainsprings and give it a service. This happen now and then with mechanical parts. I have to put it on my customers bill. πππππ