It's raining outside when Flint and his men ride into town. But when they barge into the saloon a few seconds later, the sun is shining behind them and there's no sign of rain.
In the bar when J.D. pulls the Colt Navy .44 he previously found in the sheriff's office and the cylinder rolls out, that can't possibly happen with a Colt Navy pistol as the cylinder is on a rod protruding through it's middle and extending through the cylinder with the barrel mounted on it's end. To remove the cylinder you would have to take a pin out that holds the barrel on, remove the barrel, then slide the cylinder forward on the rod to remove it. They set this up with previous dialogue in the sheriff's office when he found it, and at most one might have expected the barrel & cylinder to fall off while drawing it, which would have been more reasonable, if the pin had fell out.
In the initial shootout, Oren describes the shotgun he's holding as "sawed-off". It isn't.
Mary says the sheriff let the prisoners go before he left town. In the previous episode, a townsman identified the town's lawman as "the marshal".