some bottles definitely don't like to cap well with a wing capper, as mentioned.
Its possible that abused bottles may 'grind down' a little and not seal well.
its also possible that a really cheap wing capper's made with soft plastic that has stretched a little over time so it doesn't crimp right.
I'd like to get a bench capper cuz my wife does the capping during bottling and hates the wing job.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10