SV 8100 not disconnecting

[IT-xphones]

SV 8100 sporadically not disconnecting when the call ends. This happens several times a month.
Voltage on FiOS Hunt group line(s) is working properly. Internally the main hunt group number is busy, externally the main number rings unanswered. The full time line recorder is recording attempted unanswered calls. The calls are coming in, The PBX is not available to answer the call. Installer is pointing finger at Verizon Supervisory Disconnect.
Thank you in advance for advise you can offer.

 

[OzzieGeorge]

Might I suggest checking Command 14-02-18 as we always check this because if you don't, the VM doesn't clear down.