Gangplanks winrate has taken a dive since the most recent patch. Probably due to a bug.
Screenshot
Since the most recent patch, GP's winrate has taken a pretty steep dive. I think the main culprit is an auto attack bug. GP is already pretty difficult to play well and this makes things a lot more difficult. You miss a lot of CS and can't attack your barrels sometimes which can cost you the game. I hope riot sees this bug and hotfixes it as soon as possible because you literally can't play GP.