21xx dropping calls after 1.0.9.x



I now have multiple sites doing this at random times.
one is a 6208 running
one is a 6102 running

I haven’t put anyone on 1.0.19.x yet

After upgrading the phones to 1.0.9.x (I don’t know if it was specifically or just 1.0.9.x in general), an incoming call will randomly drop. Most often right at the moment of answering. The customer will answer the ringing call like normal and just hear a dial tone when they pick up. The person calling in simply gets hung up on.

I have contacted the SIP Provider and they say the hangup signal is coming from the other side, but I can’t trace out anything wrong other than the phones firmware.

These systems have been running fine for some time before any upgrades and I’m certain the receptionists are answering the calls normal.

Has anyone else encountered this issue since upgrading?


I have the same or possibly similar issue in two deployments. It is only on one phone in each deployment. I am on 1.0.9 as well. When the receptionist picks up the handset to answer the incoming call, the phone screen goes to the dial menu instead of answering a call. Call is lost unless it is ringing on another extension as well.

It is not happening often enough to reproduce on demand. Maybe 1 out of every 30-100 calls has this issue in my situation.,


The “other side” being the UCM or the caller side?

Does the caller call back? I assume if a true call drop, the caller will call back.

I have a number of systems on 121 and 127 and have not seen a similar issue. I have mostly 18.13, 18.16 and 19.21 installed on 61XX and 62XX, but I guess it possible that the clients may have experienced and simply ignored.

The only way to know for sure is a capture which may require setting up sftp to keep it running over time.


I’ve experienced this with 102 and upgraded handsets to 108. After a while it started again so upgraded some to 121. The issue stayed with those on 108 then started on 121!
I’ve now upgraded all our 21xx handsets to 127 and seen no recurrence.
Interestingly there also seemed to be an issue with call transfer where calls were being lost during a transfer (attended and unattended but predominantly attended) which also stopped after upgrades.
I saw this on both 6102, 6202 (mainly 18.13 now) and 3CX V15.5.


Thanks for the input, I’ll get them all to 127 and report.