When the movie studio executive is delivering his tirade to Barton Fink in the executive's office, he is wearing an army uniform. The ribbons on his chest go from being on correctly to hanging sideways from just one pin and back to their correct position all during the scene.
Note that John Goodman's ear infection switches from one ear to the other; o'course, considering the basic duplicitous nature of his character it's conceivable that he was faking it all the time, in which case ignore this NON-slipup...