BLF light status goes back to green while users on phone

[ck1]

im having some complaints from a customer that they blf light is turning from red to green even while they are still on the phone. its becoming an issues becuase the front desk will send people back when they think they are finished with a phone call, but turns out they are still on the phone. they seam to think it happens after around 10 minutes of a user being on the call. these are yealink t29g with the newest firmware and 3cx 15.5. they are configured as remote stuns behind a sonicwall firewall. 3cx is hosted in the cloud

any suggestions on where to start looking?

 

[YiannisH_3CX]

Hello @ck1

When you configure a BLF to an extension then that extension Subscribes to the extension it is monitoring. When the monitored extension gets polled then a NOTIFY message is sent to the monitoring extension which causes the BLF to change status.
For the BLF to go back to green (available) then that means that a new NOTIFY message was sent to the monitoring extension telling it that the call has ended.
That is the packet you should look for. The easiest way to do this is by running a capture and looking at the SUBSCRIBE and NOTIFY packets. As the phones are connected via STUN it could be the case that some NOTIFY messages do not arrive to the phones as SUBSCRIBE and NOTIFY messages have expire values and need updating. Make sure that each phone behind the same public IP has a unique SIP port configured and unique RTP ports. Those ports should then be forwarded to the local IP Address of the phone. https://www.3cx.com/3cxacademy/videos/intermediate/configuring-remote-extensions/