Apologies for the unclear title—I struggled to summarize the issue. If you have any suggestions for a better title, please let me know. I recently serviced this Raketa 2609.HA, and overall, I’m very happy with the results. The timing machine shows a straight graph, and the amplitude is strong in all positions—both fully wound and after 24 hours. However, I’ve noticed an unusual issue. When the mainspring is wound to about 2/3 or more, the movement starts behaving erratically in t