Updating a socket binding declaration throws IllegalStateExcp. but changes are applied

[domain@localhost:9999 /] /socket-binding-group=standard-sockets/socket-binding=test:write-attribute(name=port,value=20000)
{
    "outcome" => "failed",
    "result" => {"server-groups" => {"main-server-group" => {
        "server-one" => {
            "host" => "local",
            "response" => {
                "outcome" => "failed",
                "failure-description" => "java.lang.IllegalStateException"
            }
        },
        "server-two" => {
            "host" => "local",
            "response" => {
                "outcome" => "failed",
                "failure-description" => "java.lang.IllegalStateException"
            }
        }
    }}},
    "failure-description" => "Operation was not applied successfully to any servers"
}

[domain@localhost:9999 /] /socket-binding-group=standard-sockets/socket-binding=test:read-attribute(name=port)
{
    "outcome" => "success",
    "result" => 20000,
    "compensating-operation" => undefined
}