9611SIP phones Line appearances locked-up

[stomp192]

If anyone can shed some light here, it would be great.
Customer has CM 6.3.11 with 9611SIP phones using 5.6 firmware.
We have an on going intermittent issue. Occasionally a phone will show one or all line appearances as in use. When you push a line appearance button the phone states 'Invalid State"
Tried rebooting phone, re-registering, reloading AST config. If you login a second phone it shows the same condition.
Calling a phone with all line appearances in this state results in going to Voicemail. Options message in traceSm shows "Version 3 State = Full"
Changing the set from 9611SIP to 9611 and back Clears the issue.

[richa164]

sounds like a firmware bug to me , have you got your cm and phones on the latest firmware and checked all the PCN documents to see if this fix is explicitly mentioned.

[gwebster]

With SIP, you also need to check that Session Manager is patched to current.