PCSCF does not send 200 OK PRACK to the UE

[Ablandin35]

Hello,
A PRACK is sent by the UE after a Session Progress with TCP as transport protocol in Via, the 200 OK is correctly sent back to the UE by the PCSCF.
Then another PRACK is sent by the UE following a Ringing but with UDP as transport protocol in Via and the 200 OK is not sent by the PCSCF to the UE.
Do you know why the transport protocol is changed by the UE?
In the logs, the PCSCF seems to send the response but in fact no. Did you already experience this behavior and how to solve this?
Thanks for your support.
trace&log.zip