Connectivity issues from Public NLB to Fargate container UDP port

Yes, I have a security group attached to NLB which allows inbound and outbound traffic to 8001 port.

Can you share the task definition?

Here is my task definition:

{
    "taskDefinitionArn": "arn:aws:ecs:ap-southeast-2:xxxx:task-definition/rollover:21",
    "containerDefinitions": [
        {
            "name": "rollover",
            "image": "xxxx.dkr.ecr.ap-southeast-2.amazonaws.com/rollover:latest",
            "cpu": 0,
            "portMappings": [
                {
                    "containerPort": 8001,
                    "hostPort": 8001,
                    "protocol": "udp"
                }
            ],
            "essential": true,
            "environment": [],
            "mountPoints": [],
            "volumesFrom": [],
            "secrets": [
                
            ],
            "logConfiguration": {
                "logDriver": "awslogs",
                "options": {
                    "awslogs-create-group": "true",
                    "awslogs-group": "rollover",
                    "awslogs-region": "ap-southeast-2",
                    "awslogs-stream-prefix": "ecs"
                }
            },
            "healthCheck": {
                "command": [
                    "CMD-SHELL",
                    "nc -uzv localhost 8001 || exit 1"
                ],
                "interval": 60,
                "timeout": 50,
                "retries": 3,
                "startPeriod": 60
            },
            "systemControls": []
        },
        {
            "name": "healthcheck",
            "image": "busybox:latest",
            "cpu": 0,
            "portMap