Migrating Multi-container Docker running on Amazon Linux to ECS on Amazon Linux 2

Hi I'd like to ask if anyone was able to successfully migrate their existing Multi-container Docker running on 64bit Amazon Linux which is about to be deprecated to the newer ECS running on 64bit Amazon Linux 2?

I followed the steps outlined in this document: https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/migrate-to-ec2-AL2-platform.html using the AWS CLI to upgrade our environment. It did upgrade it to the new platform however I'm getting a 502 Bad Gateway in my webpage.

The document says no configuration needs to be changed on the source code as well as in the Dockerrun.aws.json v2 file. Is there any additional configuration I'm missing? When I rolled-back the platform to the previous one (Multi-container Docker running on 64bit Amazon Linux) - it went back to normal.