[Asterisk-Users] Phone always busy after caller hangup

[Tim P]

I have multiple sipura 2100 boxes connected to my * box and for some
reason that i cannot figure out when making a call to one and
answering it and then hanging up results in the line be permanently
busy (the phone called is permanently busy until * is rebooted).  Any
idea where to start with this one?  It seems to me that either the
SPA2100 is not registering the end of the call or * isn't.  I suspect
the SPA2100 but see nothing in the logs or in the SPA config to
indicate a fix.  Any ideas?