I also found something that might be of some help. Under the status of a working phone, I found the following entry in a section called "Actor Data":
State:Idle;Msg:messageWaitingI
ndicator;Port(Id):pDeviceInter
fac
On a phone that is not working, I found the following:
State:Active;Msg:endSession;Po
rt(Id):pDeviceToSession(0);
Notice how the first mentions a message waiting indicator.... Do you think this has anything to do with it?