i thought that too and so i shaken a couple to see if they would leak and they did not. I do use an antique capper but it has worked in the pass maybe its time for a new one.
Primary #1: Empty
Primary #2: Empty
Future: Robust Porter
Future: Breakfast Stout
Future: Imperial Pale Ale
Future: Belgium Triple Ale
Did you rack your beer to the bottleing bucket and then add the priming solution?
or even better give us a history of everything you did from fermentation on. Including temps ect.
I put in the priming sugar then i started to siphon the beer into the bottling bucket