Internal Auto Answer set to intercom does not release calls

We have a site running 6-12-65-27 vs 12.0.63
Have 2 stations with Yealink T48G phones both set to Internal Auto Answer=Intercom and not all the time but most of the time the connection remains open even if one of the station ends the call.
The most recent calls show 17 minutes and 22 minutes of activity in CDR when I look at the PCAP they both show that the RTP Stream ends 266 and 301 seconds sooner then the last SIP Packet.
We have other VPS running the same 6-12-65-27 software and Yealink phones with out this problem ?
As a FYI this site has a Sonicwall Router ( managed by the company IT company) we had many issues and have been able to resolve some but this seems to come back .
I changed the conference room setting to =app_meetme CDR show ConfBridge and *80xxx ( ext number)
The problem that is reported is always between the same 2 extension.
Any help on this would be greatly appreciated

This is happening on extensions that are VPS and BLF is set to each extension- also in FreePBX (server -extension setting i set to Internal Auto Answer =Intercom)
Hopping that I can get some help on this issue.
I have tried testing and with other phones on same VPS and have different results and they work as they should
When I look at the CDR its showing *80xxx =*80 is the feature code for Intercom prefix But CDR Shows ConfBridge
I have tested other Yealink phones and the same setting does not set call as a *80xxx. They just dial the ext number (the CDR show it is just a dial not a *80xxx) and the auto answer on intercom and it open the path and if either party hangs up it releases the call.
Example of two stations that are the problem if ext 100 calls ext 101 with the DSS/BLF key when ext 101 leaves the call ext 100 stay connected (just like if it was connected to conference bridge and when you press the speaker key or handset pickup and hangup) it then terminates call.
That is the issue that I am trying to resolve-1 what is causing it to become a conference bridge call and why if called extension hangup why is the caller party stays active 2-If I dial *80xxx manually it either party disconnects both ext disconnect and CDR does not show it as ConfBridge ?
Thanks in advance