"transport=tls" not set in Contact header

[Jannick-O]

Description:

I'm trying to set up FreeSWITCH using TLS.
SIP-Trace shows the device registering through TLS.
When receiving a call FreeSWITCH receives an INVITE through TLS. FreeSWITCH replies through TLS, however the header "Contact" does not contain "transport=tls". Because of this, the other system tries to reply on port 5060/UDP, which leads to a timeout.

Is this just due to poor configuration or is there a bug in FreeSWITCH? Are there any additional configurations that have to be set for this to work?
If additional information are needed please let me know.

Relevant configuration:

<profile>
    <settings>
        ...
        <param name="tls" value="true"/>
        <param name="tls-only" value="true"/>
        <param name="tls-bind-params" value="transport=tls"/>
        <param name="tls-sip-port" value="5061"/>
        ...
    </settings>
</profile>

SIP

The following SIP message is received by the other system, "Contact" does not contain any transport parameter:

SIP/2.0 200 OK
Via: SIP/2.0/TLS <REMOTE_IP_REDACTED>:5061;branch=z9hG4bK135eaa83229cfdb;rport=42881
From: "Caller" sip:<REMOTE_PHONE_REDACTED>@<REMOTE_IP_REDACTED>;tag=68467534~cad25b0a-1afc-4dfb-b28f-f4443b6e21fd-43228853
To: sip:<FREESWITCH_PHONE_REDACTED>@<FREESWITCH_IP_REDACTED>;tag=NNBvQNvB8amSQ
Call-ID: 2b687400-1f016c4e-11ee423-48c2b0a@<REMOTE_IP_REDACTED>
CSeq: 101 INVITE
Contact: sip:mod_sofia@<FREESWITCH_IP_REDACTED>:5061
User-Agent: FreeSWITCH-mod_sofia/1.10.9-release+git~20230203T200730Z~a615e85afc~64bit
Accept: application/sdp
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
Require: timer
Supported: timer, path, replaces
Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
Session-Expires: 1800;refresher=uac
Content-Type: application/sdp
Content-Disposition: session
Content-Length: 613

v=0
o=FreeSWITCH 1722304963 1722304964 IN IP4 <FREESWITCH_IP_REDACTED>
s=FreeSWITCH
c=IN IP4 <FREESWITCH_IP_REDACTED>
t=0 0
m=audio 22058 RTP/AVP 102 103 104 9 0 8 105 107 101
a=rtpmap:102 opus/48000/2
a=fmtp:102 useinbandfec=1; maxaveragebitrate=64000; maxplaybackrate=48000; sprop-maxcapturerate=48000; ptime=20; minptime=10; maxptime=40
a=rtpmap:103 SPEEX/16000
a=rtpmap:104 SPEEX/8000
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:105 telephone-event/48000
a=fmtp:105 0-15
a=rtpmap:107 telephone-event/16000
a=fmtp:107 0-15
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20