Problem with HMR to drop 183 when no SDP

I am testing a Verizon SIP trunk configuration with Lync 2013 (simple enterprise trunking model).  For early media (using SBC PRACK interworking code) on inbound calls, Lync sends an initial 183 with SDP which works fine (SBC responds with a PRACK, etc).  However, Lync subsequently follows this with a couple more 183’s without SDPs before the call setup is completed and Verizon does not accept this behavior from Lync – they want us to eliminate those 183’s without SDP. 

 

There is an HMR example to do exactly this in the E-Cx6.4.0 ACLI Config Guide (Nov 2013) – example 9 on pg 388 -- so I configured this per the documentation (we are running on E-Cx6.4.0m2).  First I had to fix the HR named “IsContentLength0” because it was resolving to true whenever the content-length value included a zero (for example 250) vs. being