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CSCvs10565 - CUCM ignores ACK for a Re-INVITE if it gets any intermediate UPDATE before the transaction completes

Hey All,


We are currently experiencing this bug in a production environment. What's happening is anytime Cisco communicates with a third party sip vendor that happens to send 2 UPDATE's before Cisco respond wigs Cisco out and it will start treating the call as one-way conversation. The specific use case for our organization is anytime Phone A (Cisco)  is transferred from Phone B(3rd Party Voice System) to Phone C (Same 3rd Party Voice System) One Way Audio will occur and the call will actually automatically shut down after 15ish seconds.


We have a HA cluster for CUCM that is on the latest update from 12.5. What happens is cisco receives the UPDATE packet for the transfer to Phone C and before Cisco responds receives a second UPDATE packet. Cisco now ignores and does not acknowledge the UPDATE and treats the call as a 1-way no audio needs to be sent from Cisco. 


Cisco released a "fix" for Version 14 which has no release date but is rumored for mid 2020. Our organization has this bug happening on a daily basis for calls. We are in the middle of migrating from the 3rd party phone vendor to Cisco but would have to replace around 5000 phones in order to eliminate the old system.


The normal scripts won't work as it modifies SIP headers but not call flows. Does anyone know of a way to modify or force cisco to accept the call flow? Or how we could maybe create a band aid until Version 14 is released? 


Thanks for your time.