rammus W canceling itself?

Playing rammus, everything great for 3/4 of the game, I die with 5k like 16 mins in, I buy the warmogs and a chainmail destined for a dead man's plate.... and suddenly my W stopped working. I'd engage, and every time I hit W, it would immediately go on CD, but my shield would only flash up, like I was immediately canceling it. I die 3x straight doing this... I get my biggest 5k buy and suddenly, randomly become ezpz to kill because my W broke. It repeated itself the rest of the [formerly won, now unavoidably lost] game.

As a side note, how do I record what goes on in a game? apparently there's a playback option?

game in question matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2542990952/238002589