So, this fight has a "trap", in that investigating the caskets will spawn a skeleton, and it proceeds to run to the next casket and summon it's fellow bone buddies.
The bug specifically here is that once the first coffin is activated, the others will not trigger in the same fashion if you kill the first skeleton before it can summon another (I was sneaking, and shoved the fellow off a cliff). These essentially creates an encounter where only one skeleton spawns and you are unable to summon and deal with the rest.
