2 different sip client have same cookie in registration cache

hi all,

We have a strange issue about client registration cache. Our agents ( around 400 agents ) are coming from internet and register to internal servers. When 2 agents send register request , acme sbc create same cookie for these 2 agents and insert that to contact header. These 2 agents register to different registrar servers. And when these agents make outbound or inbound call , their calls mixed and hear each other. This problem occurs randomly. When one of the clients re-registers a few times, the cookie changes and the problem is fixed. I also open SR but