WebMethods not sending ACK/FINISH to IIS Web Services calls

We've repeated this one in Test, so I like making this inquiry - not that I comprehend it or anything. ;- ) 

WebMethods is interfacing with an IIS Web Service (I'm the IIS fellow, and the WebMethods fellow has no response for me.) IIS is tossing 200 0 1236 mistakes on a large portion of the calls, however. The reason for that is Timer_MinFileBytesPerSec. WebMethods is content with the outcome IIS sends, and doesn't generally close the system discussion amenably. This isn't an issue until the point when we get two brings in flight in the meantime. On the off chance that IIS kills the principal convo for MinBytes it will kill all open convos with that IP address, accordingly killing the second discussion in passing. WebMethods vomits on that mistake, and I get called. 

Is there any approach to compel WebMethods to end the system discussion courteously?

Failed convo:

WebMethods sends SOAP in 2 packets - SOAP + HTTP continuation
IIS sends ACK
15 second processing delay
IIS sends SOAP reply with ACK/PUSH/FINISH flags
WebMethods sends ACK flag
15 second delay
IIS sends Reset flag and conversation dies

Successful convo:

WebMethods sends SOAP in 2 packets - SOAP + HTTP continuation
IIS sends ACK flag
15 second processing delay
IIS sends SOAP reply with ACK/PUSH/FINISH flags
WebMethods sends ACK flag
6 second delay
WebMethods sends ACK/FINISH flag
IIS sends ACK flag
We all go home happy

If I extend the ConnectionWaitTimeout and HeaderWaitTimeout on IIS and contract the MinFileBytesPerSec setting, I can make IIS wait indefinitely for WebMethods to politely send the ACK/FINISH, but it never comes.