What if whenever the winter soldier code was read infront of Bucky, he tried to scream and scream and SCREAM so he couldn’t hear the words? So he wouldn’t be ‘put under the spell’? What if he screamed his throat raw? What if that’s the reason he had to wear a muzzle?
I actually had a long discussion with my boyfriend about this because we were trying to figure why Bucky didn't just cover his ears or yell to drown it out and then it occurred to me: Bucky had those words repeated to him numerous times, enough times that it became a literal reset. So I figured once he heard the first 2 maybe 3 words (and really that's when he realizes what's going on) its probably so engrained in his mind that even if he did yell his own subconscious would finish the words anyway causing him to reset.