I've got a hunch - and I think verv might have said this somewhere - that the issue is likelier the more the watch is worn. My (very early, so out of warranty) SD43 has always been 1-2 seconds per day slow. This thread induced me to check it again and it lost 2 seconds in two days - pretty good. But it's only occasionally worn, so if the issue is something to do with wear and tear, loss of lubrication etc, you'd expect that.