On occasion when attempting to plan an outbound call, some extensions will get a buzzing sound immediately after dialing. If they hang up and try the call again, it will usually go through. This doesn’t happen on all extensions and only happens to maybe one it 25 calls and only outbound. All extensions are PJSIP and the provider is Flowroute. The phones are Panasonic KX-TPA50 or Panasonic KX-TPA60. When looking at logs, I can see the call go from the extension to Freepbx and then go out through the Flowroute trunk (and when looking at Flowroutes logs, I see the call with only a few second duration and no error on their end). FreePBX 15.0.37.4
You can hear the sound here (recording from FreePBX system)
Any ideas/suggestions on how to troubleshoot are welcome and thanks in advance!