What time is it? Watches and horology

I've also got a watch in need of service/repair. SKX007 (nearly 3yo), which no longer runs - I can hear it winding, the crown works fine to set date and time but the only time the second hand advances is when the watch is shaken. It literally stops as soon as it's still.
What's the probable diagnosis?

No one cares, but hopefully it'll help someone out in future - Turns out the winding rotor wasn't spinning freely and I think was catching on the case back. Tried to tighten the central screw holding the rotor in place and loosened off the case back a little and that seems to have sorted it.