Looks like this is limitation of HTTP Protocol with large payload. We used to get the same problem even with custom code written to do HTTP Post. Fortunately, in our case the other party used to get our orders but somehow their web server returned this error inspite of fully receiving the payload.. We could not do anything but to catch this exception and proceed with other logic…
Please post here if you happen to solve this problem in a standard way. It will help all of us.