Challenge with ECS Service Connectivity in Bridge Network Mode within Private Subnets

I'm encountering connectivity issues while deploying ECS services in bridge network mode within private subnets.

The architecture involves a mix of internal and external services, where awsvpc is preferred for internal services due to its advantages in service discovery, and bridge mode is chosen for external services to leverage the load balancer. This approach is driven by the need to deploy 14 services, and using awsvpc for all could lead to ENI exhaustion. While the configuration works seamlessly in public subnets, services fail to connect when EC2 instances are placed in private subnets. Despite having a NAT gateway as the default route for private subnets, the connectivity remains unresolved.

Seeking insights and solutions to enable efficient communication for ECS services in bridge mode within private subnets.