When installing or editing a container, if there are any conflicts (or if another error happens which prevents starting), it will appear in the docker run command which is listed.
If just starting an already installed container and due to a conflict / error it won't start you'll see "Server Execution Error", at which point you can easily see that actual issue by editing, make a change, undo the change and then hit apply
As an aside, 6.10 when changing any of the ports in the UI does a check to see if the port is already in use and won't let you apply the changes.