Skeletons don't die

Skeletons occasionally don't burn in sunlight. They show hurt particles after the first time you hit them but not on subsequent hits. You can walk through them. Dogs are still attracted to them. They don't fire at you move at all. Arrows bounce off them. Restarting the game makes them go away.

EDIT: The screens are from an old snapshot, but I have observed the issue in 46a.