Other mistake: Raylan fires two shots into the above-ground pool, but it springs three leaks. Looking closely it does appear that Timothy Olyphant squeezed the trigger three times, but one blank must have misfired, and the three squibs went off regardless.
Walker: You shot me in the back!
Raylan Givens: You wanted to get shot in the front, you shoulda run toward me.
Question: Mags poisons herself with the same "it was in the glass, not the jar" approach she took with Loretta's father. But we see her grab two glasses - one from the cupboard and one off a shelf. Does she slip poison in while off camera, or is it just that the cupboard/shelf glasses are always poisoned, trusting that everyone knows not to use them? Seems like a crazy risk to take.