Cisco 9951: unanswered calls sticking

I suspect this is more to do with phone configuration than Asterisk, but I have my fingers crossed someone else from these parts has hit this one before.

Cisco 9951 running 9-2-x - 9-3-x firmware presents with a hanging “missed call” on the screen. All unanswered calls result in the phone keeping an inaccessible line on the screen. Another interesting symptom is when a bluetooth headset is connected the phone appears to leave the headset hanging in an “incoming call… beep beep beep please answer” state. The phone recognizes when the call has ended as far as I can see, and even removes the incoming call icon from the line once it has ended:

<— SIP read from TCP:162.123.123.123:51394 —>
SIP/2.0 487 Request Cancelled
Via: SIP/2.0/TCP 10.0.145.10:5060;branch=z9hG4bK7f1e79ca;rport
From: sip:+18005551212@10.0.145.10;tag=as58c2f2da
To: sip:200@10.0.0.140:51394;transport=tcp;tag=d0574c6a959c00063aadbc82-56e7cbff
Call-ID: 25bc9b8457312966092e13d954fedf2d@10.0.145.10:5060
Date: Wed, 11 Dec 2013 07:30:19 GMT
CSeq: 102 INVITE
Server: Cisco-CP9951/9.2.1
Contact: sip:200@10.0.0.140:51394;transport=tcp
Allow: ACK,BYE,CANCEL,INVITE,NOTIFY,OPTIONS,REFER,REGISTER,UPDATE,SUBSCRIBE,INFO
Allow-Events: kpml,dialog
Content-Length: 0

<------------->
— (12 headers 0 lines) —
Transmitting (NAT) to 162.123.123.123:51394:
ACK sip:200@10.0.0.140:51394;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.0.145.10:5060;branch=z9hG4bK7f1e79ca;rport
Max-Forwards: 70
From: sip:+18005551212@10.0.145.10;tag=as58c2f2da
To: sip:200@10.0.0.140:51394;transport=tcp;tag=d0574c6a959c00063aadbc82-56e7cbff
Contact: sip:+18005551212@10.0.145.10:5060;transport=TCP
Call-ID: 25bc9b8457312966092e13d954fedf2d@10.0.145.10:5060
CSeq: 102 ACK
User-Agent: Asterisk PBX 11.6.0
Content-Length: 0

Is there some option within the xml that removes missed calls from the screen?