ANet didn't think about bad connections...
The better solution would be not to have a loading screen between the waiting area and the actual jumping puzzle. They could just have you wait in that initial area (without the damage of course) until the “round” starts.
I had this same problem with the Clock Tower but apparently ArenaNet didn’t listen.
I’m not even going to bother with the Wintersday puzzle if it’s the same, which it sounds like it is.