AWS ECS Fargate request not reaching task container - amazon-web-services

Question

So I setup a aws ecs cluster to run a docker image of Valhalla service almost as-is.
Issue : target group seems to be not able to check for cluster health, like if the health request was reaching the cluster, but container is not "forwarding" the request to Valhalla.
Description :
I created a repository on AWS ECR, and pushed a docker image of gisops/valhalla with only the valhalla.json file changed.
Here is the valhalla configuration I used.
Note that I changed the default listening port from 8002 to 80.
I created a ECS Fargate cluster, and a service that uses this task definition to launch a container that runs Valhalla.
The service receives traffic from an application load balancer via port 80.
The target group is checking /status path on port 80.
All set, the task is then creating, and task logs shows that Valhalla is initializing perfectly and running.
However the target group is not able to check for health status : the request seems to timeout.
If the request was reaching valhalla, the task logs would have at least show it (because valhalla logs every incoming request by default), but it doesn't.
Therefore fargate kills the task (Task failed ELB health checks in (target-group {my-target-group-uri})) (showing that the health request was reaching the cluster service indeed)
I don't think the issue is with the valhalla configuration, because I can run the same docker image locally, and it works perfectly, using :
docker run -dt -p 3000:80 -v /local/path/to/valhalla-files:/custom_files/ --name valhalla gisops/valhalla:latest
And then checking localhost:3000/status
Anyone has an idea of what could be the issue ?
Already spent a lot of time on this, and I'm out of ideas. Thanks for your help !