Monster infighting between passenger and rider

Mobs will, if aggravated, become hostile towards and attack their rider or passenger.

This is typically observed when a skeleton shoots its spider mount. Fixing MC-88491 would make this behavior less frequent, but the underlying issue remains.

You would expect mobs riding each other to "cooperate" and ignore any accidental attacks that happen to occur. In their current form, spider jockeys are incredibly unstable, as one misfired shot results in the stack entirely ignoring the player, opting instead to jump around trying to kill itself as quickly as possible.