On the levels where you unmask the words

My game is in english. I will choose the correct mystery letter and it will not count. Maybe if it has a vine this is why. But many times i must choose it again. This becomes very confusing. You think oh well maybe it’s not the word I think it was and then it ends up being the word you thought it was this game has some very crazy turns.  Honestly I really hate the mystery word challenges .  I cannot speak to specific levels that I have managed to finally work my way through always let it happens quite often.