Action On Service Down - expected results

Disabling a node means that the node can only handle persistent (requests for which there's a persistence table entry) and active (TCP) connections. Forcing the node down means that it can only handle active TCP connections. Neither option will "kick" an active TCP connection from the node. So your errors are very likely coming from the fact that you're simply turning off the server before active TCP connections have had a chance to bleed off. For HTTP traffic this shouldn't normally be very long. You might want to consider adding a looping check to make sure there are no active connections before moving on to turning off the server.