Stupidity: Hungarian Police Lieutenant Benedeke Erdös has broken right arm in a cast. Although his arm is in a cast, he is still in uniform and carrying his firearm in a holster on his right side. There's no way he can draw the weapon or secure it. (00:20:45 - 00:21:19)
Nothing Sudden About It - S4-E3
Other mistake: The agent reaches into a toilet tank to retrieve a wristband. He holds the wristband up to look at it, and his hand isn't wet. (00:25:47)