serversTransports serverName not working when Traefik runs in Container

Hi,
I'm running Traefik in a Docker container using docker compose.
When I try to connect to my service, I get

level=debug msg="'500 Internal Server Error' caused by: x509: certificate signed by unknown authority"

In the dynamic conf I set

[[tls.certificates]]
  certFile = "/etc/ssl/fullchain.crt"
  keyFile = "/etc/ssl/privkey.key"

[http.serversTransports.myservice]
  serverName = "service.com"

and the service container is labled with

"traefik.http.services.gitlab.loadbalancer.serverstransport=myservice@file"

This setup works, when I just use the Traefik bin and don't run it in a container.
From within the container it works, when I add

insecureSkipVerify = true

to the serversTransports.myservice.

Sounds like the crt and key file might not be mounted/included in the container properly, particularly if it works with the traefik binary direct.

I simply mounted the files folder into the container. Traefik can find the files, read the domains and does the ssl termination correctly.

Aaah no, Traefik in the container can not find all certificates. I have to provide the rootCAs. Using the Traefik binary, is already on the machine