In a vanilla game, COC from the main menu to RiverwoodSleepingGiantInn, exit the inn and go all the way up to the Helgen cave entrance. From there, go south to a camp of three or four bandits, they'll react just the same. There will be at least one bandit stuck in an endless sheat/unsheath loop from distance until you get close enough for them to attack.
Guess is that it is due to filling NPC aliases without doing anything to the alias but need to track down the quest doing this.