In coming call returns No Anser

In our network, we are seeing a problem with an incoming call whereby the Asterisk returns back to the originator Busy; however, the terminator is not on their phone. The originator may try again and the result is success at times and others continued busy.

The interesting thing in the CDR is the Destination Context is equal to “default” in these cases alone, the dstchannel is blank, the lastapp is equal to “ODBCget” and lastdata is equal to “server=SERVER/”.

Below is a failed CDR:
‘11,349,815,485,183’,’ ‘,’ ‘,’’,’’,‘default’, ‘"" <>’,‘SIP/plc-28d3’,‘ODBCget’,‘server=SERVER/’,‘2005-12-19 09:39:08’,‘0’,‘0’,‘1’,‘3’

Below is the passed CDR immediatly after the passing one:
‘11,349,815,835,195’,’ ‘,’ ‘,’’,’’,‘int_cfbs’,’"" <>’,‘SIP/plc-676e SIP/62227723-de6b’,‘Dial’,‘SIP/62227723|180’,‘2005-12-19 09:39:43’,‘10’,‘3’,‘ANSWERED’,‘3’

I am having trouble identifying why the destination context values are different and the meaning to the lastapp value, in addition to the other issues.