Fix error 'no shared cipher' when receiving incoming call by Firefox 39 - Sipjs WebRTC

I'm using [login to view URL] ([login to view URL]) with Asterisk 13.3.2 to build a webphone for our CRM. Everything was working perfectly before. However, when Firefox 39 released and updated automatically, i have been facing problem of receiving call by Firefox. When using Firefox-39 to make call other client, it's still work normally but when using Firefox-39 to receive call, it says (from asterisk console): "[2015-07-16 23:03:32] ERROR[7476][C-00000001]: res_rtp_asterisk.c:2042 __rtp_recvfrom: DTLS failure occurred on RTP instance '0x7f0ee40067d8' due to reason 'no shared cipher', terminating" Again, chrome, opera, firefox 38 and older was working perfectly. I also dont think there is something we can do with sipjs to solve the problem, just trying to find a way to configure something on Asterisk to fix it. I'm willing to pay for a commercial support on this.