I use a bench top capper and never had a miss-sealed cap with the twisty bottle. I recommend giving the bottle a quarter turn after depressing the capper and giving it another go. Saw this method online and it consistently gives that round dimple in the middle of the cap.
Thanks for the responses, il just have to see how it goes, I put some soft drink in one bottle and capped it, it didn't leak any gas so fingers crossed, now to put another batch down.