ZTNA with SIP over TCP

Hi,

I am getting serious crazy with an issue with ZTNA.

Setup: I have two Fortigate, (Site A) and a Fortigate (Site B) with an IPSEC-Tunnel between.

I know I have to work with ZTNA IP pool to reach out a destination on Site B.

I want to have port 5060 (TCP) reachable over a TCP ZTNA Setup. I know, I have to setup Endpoints on the EMS, too.

Fortigate does have FortiOS 7.2 running the latest Patch, EMS 7.4.1 on the Cloud.

Test: Port 3306 for MySQL: works (TCP, not encrypted)
Test: Port 22 for SSH, works
Test: SIP, TCP 5060, DOES NOT WORK

I already disabled the SIP helper and tried with other incoming ports, nothing works. TCP with SIP works on the local VLAN indeed.

If there is anyone with a good idea, I am here ;)

Thanks