Yes, well... the others (other instances) returned None. Say you run an Action and have two instances. One of them fails, the other succeeds. Because the first failed the Action becomes available. If you run the Action then the other instance will still be iterated and would have
result["error"] is None so you'd have to ensure you're catching that.
Similarly in any Action the
result["instance"] is None at least once because of the "Context" being iterated (if I understood @tokejepsen correctly). I think this is new behavior since I can't recall having that problem before.
Does that help?