REST call to stop/restart a container overrides the default stop timeout (before kill) with hardcoded 5 seconds.
Containers already have a default stop timeout handled by the engine API (https://github.com/moby/moby/blob/master/client/container_stop.go).
With this hardcoded 5 seconds, the containers get killed after 5 seconds even if they define a custom greater stop timeout.
Another solution would be to not hardcode the 5 seconds but rather use a global editable setting.