When you try to actually connect to the game, the game tries to connect to the default query port to get all necessary information on port 2457 and the query port actually responds with a message to the game that the game port is on 2456 and then a connection is established.
Take Valheim for example, the default game port for example is 2456 (game port) then there is the port 2457 (query port) and the port 2458 (I don't know what it's exactly for but if you close it you cannot connect to the server). No, this is not the case with every Docker template but game servers are not normal Containers in terms of port forwarding. Is there a reason that you have to delete the port configs and cannot just change them? Is this the case with every docker template? Would it be better to change all the ports in the settings files or is this the right way to do it? (I only found the RCONport line in the settings) I added the following parameters and changed the RCONport RCONportin the gameusersettings.ini and afterwards it worked.
Is there a reason that you have to delete the port configs and cannot just change them? Is this the case with every docker template? (First time I duplicated one) Keep in mind that it isn't enough that you just change the host port if you click on a port entry in the template and change that, thats also the reason why you are in the old instance.
You have to change the Name of the Container, the path to the Game Files (the path to SteamCMD can be the same), you have to change all the ports in the config files so that they don't match the other server (all of them) and then you have to delete all port entries in the Docker template and create new ones that are match the new ports that you have in your config files.