One more docker with identical config leads to Gateway tiemout for that docker

Hi @wisbit and @Anonymous-Martian,
Thanks for you interest in Traefik.

The 504 - Gateway Timeout error often occurs when the service is not accessible from Traefik.
In case of multiple networks, Traefik does know which one to use. You can have a look here.

NOTE: The label described in the linked answer is also available on a per-container basis.