How to remove an expired contact from reg-cache?

Hello,

I fixed the problem described in bug id 34936817 "High amount of AAR requests sent towards PCRF" and got a new problem instead after upgrade SCZ9.1p4 -> p7:

When VoLTE bearer fails, an SBC gets ASR command via Rx interface for a particular subscriber record, it changes the status of the record to "EXPIRED" in the cache. As you know, expired records live for some time before SBC removes them completely, I assume SBC keeps them inside for 30 seconds.

If subscriber re-establishes VoLTE connection within aforementioned 30 seconds and sends REGISTER from new IP address, then SBC adds this new IP address as a second Contact into expiring record in the cache. So the REGISTERs forwarded to the Core contain two contacts: expired and new. The Core does not expect such behavior.