Recently I came across an issue with a new customer deployment where the 9951 SIP phones would drop call after 18s. All other SCCP phones were working fine but only these SIP phones would drop the call.
Call flow:
9951 -> SIP -> CUCM -> SIP -> CUBE
Bind commands were in place and the only way I could resolve the issue was forcing RTCP parameter “disabled” under Common phone profile and Enterprise Phone parameters.
System -> Enterprise Phone Configuration
AND
Device -> Device Settings -> Common Phone Profile
RTCP
DISABLED
voiceonbits.com 
Did you stop updating the website? Your tips are very helpful!
Can you please elaborate it.
I went over this web site and I think you have a lot of
fantastic information, bookmarked (:.