Symptom:
Proxy free routing statistics does not work when "custom volte screening" is used

Conditions:
UAC and UAS are registered with CISCO-P successfully
Enable "proxy-free-routing", "proxy-free-paging" in P-CSCF context
CISCO-P looses UAC,UAS information and has proxy-free routing, paging CLI enabled
UAC sends INVITE to CISCO-P 
Orig CISCO-P routes the call to Telco-P at the originating side
Term CISCO-P routes the call to Telco-P at the terminating side
Telco-P sends 100 Trying/180 Ringing/200 OK to CISCO-P
Call is established and torn down successfully
"show cscf sip stateless-proxy statistics name proxycscf" does not display profy free routing statistics 
Now do "no custom volte-call-screening" under PCSCF context even though it was not enabled earlier and run the same case 
Now "show cscf sip stateless-proxy statistics name proxycscf" displays proxy free routing statistics

Expected  Result
"Invite Routing" count under "show cscf sip stateless-proxy statistics name proxycscf" should be updated

Actual Result
"Invite Routing" count under "show cscf sip stateless-proxy statistics name proxycscf" is not being updated