Other mistake: Even when not referring to his own emotions, The Collector can't say the word "love" when he is trying to seduce Jeryline at the end. He tries very hard to say it, but is simply incapable of using the word. Earlier, when The Collector was tempting Cordelia, he used the word several times without issue.
Revealing mistake: Brayker shoots The Collector through the eye with an arrow just after he's collected the key from Roach. You can see the section of the arrow shaft that sticks out the back of The Collector's head bend as his head hits the floor after he falls over the upstairs railing and crashes through the coffee table.