I tried your test suite, but it failed for two of the methods, one being testNBSenderInOutAsync()
Looking closely into it, I think you are using the ServiceClient.sendReceiveNonBlocking() to call an InOnlyAxisOperation which is wrong.
I agree that when a 202 accepted response is received that the ClientHandler should not look for the MR to pass it back, but I am having trouble now trying to understand what exactly is the problem we are trying to solve..
I am guessing your Mac OS may have something to do with any intermittent errors you are seeing, but on my Linux (Ubuntu) system, I do not see any other exceptions when I do the following:
sender = new ServiceClient(asyncConfCtx, null);
Options options = new Options();
for (int i = 0; i < REQUEST; i++)
OMElement method = factory.createOMElement("asyncEcho", omNs);
OMElement value = factory.createOMElement("myValue", omNs);
value.setText("Isaac Asimov, The Foundation Trilogy");