Installation of ECE 3.7.3 "finished" with errors

Hello,
I'm trying to deploy an ECE 3.7.3 onprem following exactly the deployment guide at elastic.co. Regardless, which OS I choose (RHEL, Ubuntu, Rocky) the installation starts without any issues. While security-container deployment I can see in the logs some timeouts but the installation continues with logging-monitoring finishing with an error message.
I'm then able to log into the admin console everything showing green.
Thing is: Creating my own deployments lasts ages (1-2 hours). Log into those deplyoments failed with error "application could not be loaded"
Could you share some troubleshooting steps, e.g. which logfiles are worth checking?
As for the setup: small deplyoment with 3 hosts (VMs), 128GB RAM each, 500GB HDD each with XFS incl. quotas, cgroups v2 disabled - so everything according guidelines. RHEL/Rocky with podman gives the same results as Ubuntu with docker.
Thanks