I just serviced a Vostok cal. 2431 in overall very good condition. I've had it since it was new (2014) and it was performing reasonably well before servicing it. It's identical to the cal 2416B but has been modified (by Vostok) to make the hour hand rotate 360 degrees only once per day (24h movement). Anyway, in the process, I carefully adjusted the end-shake to be as small as possible while carefully making sure all wheels were spinning freely. After the service, the amplitude became extre