Peter there are amultitude of posts about 7750 seconds at 6 and the reasons why it stops
In short the movement has a number of transfer gears to move the seconds from 9 to 6 these have too much friction due to no jewels fitted, it is an engineering example of a flawed idea, there are fixes, but non are totaly proven, non are cheep, take a week off and search and read, (it will take you that long, the daytona's have the same issue)
And that is the reason i dont have a 3714, even though i love them just like you. As a stock rep it is not great apart from on the shelf to look at.