Extensions were still busy!

General Help
1

Dear Sir,

I have a strange problem in FreePBX Distro (2.10).

more than 400 phones are registered and work fine with the server.
BUT sometimes (one or two times per day), When a caller calls to a callee, and after that the caller end the speaking and pick down the phones, Asterisk does not send the HANGUP request!!. so with the command “sip show channelstats” I see two extensions that are talking about 23:10:50. (the connection does not HANGUP)
also, in this situation, Caller and Callee, both of them are still busy. and I had to send a command manually to HANGUP the connections. “channel request hangup sip/xxxx”

most of the phones are SNOM300 and YEALINK T22.

Could you please help me.
Thank you guys.

2

Have same issue, 100 extension with yealink t20, freepbx 2.11, at least one in month I need to do manuly soft hangup for extension remain inuse or active channel. RTP timers does not give results.