Snom drop call

Hi
I have an issue with snom 370 drop a call by sending BYE

|Time     | 10.10.2.121                           |
|         |                   | 10.10.2.153       |                   
|16:56:35.270560|         INVITE SDP (g711A g7          |SIP From: "Op1" <sip:2121@10.10.2.153 To:<sip:*2126@10.10.2.126;user=phone
|         |(1024)   ------------------>  (5060)   |
|16:56:35.271002|         401 Unauthorized              |SIP Status
|         |(1024)   <------------------  (5060)   |
|16:56:35.325709|         ACK       |                   |SIP Request
|         |(1024)   ------------------>  (5060)   |
|16:56:35.353615|         INVITE SDP (g711A g7          |SIP From: "Op1" <sip:2121@10.10.2.153 To:<sip:*2126@10.10.2.126;user=phone
|         |(1024)   ------------------>  (5060)   |
|16:56:35.354577|         100 Trying|                   |SIP Status
|         |(1024)   <------------------  (5060)   |
|16:56:35.355148|         200 OK SDP (g711A g7          |SIP Status
|         |(1024)   <------------------  (5060)   |
|16:56:35.455150|         200 OK SDP (g711A g7          |SIP Status
|         |(1024)   <------------------  (5060)   |
|16:56:35.498055|         ACK       |                   |SIP Request
|         |(1024)   ------------------>  (5060)   |
|16:56:35.713967|         RTP (g711A)                   |RTP Num packets:372  Duration:7.449s SSRC:0xD6CA85F4
|         |(50570)  ------------------>  (13208)  |
|16:56:35.727583|         RTP (g711A)                   |RTP Num packets:400  Duration:7.980s SSRC:0x70F2A5BF
|         |(50570)  <------------------  (13208)  |
|16:56:36.297518|         ACK       |                   |SIP Request
|         |(1024)   ------------------>  (5060)   |
|16:56:43.719055|         BYE       |                   |SIP Request
|         |(1024)   ------------------>  (5060)   |
|16:56:43.719384|         200 OK    |                   |SIP Status
|         |(1024)   <------------------  (5060)   |

I changed into sip.conf
session-timers=refuse
session-expires=10800
session-minse=300
session-refresher=uas

but I can se that Expires sent by asterisk is 3600 so may be I have to change maxexpiry=3600

Any idea ? :question:

This could also be an interop-problem from snom. Which firmware is active on the 370? Which Asterisk-version is in charge?