Cannot restore default for Unhealthy target connection termination

[Moulick]

Bug Description
Cannot disable "Unhealthy target connection termination" once enabled via service.beta.kubernetes.io/aws-load-balancer-target-group-attributes

Steps to Reproduce

1. Set service.beta.kubernetes.io/aws-load-balancer-target-group-attributes: target_health_state.unhealthy.connection_termination.enabled=false,target_health_state.unhealthy.draining_interval_seconds=30
2. Check that the attributes have been updated in the NLB listeners
3. Set service.beta.kubernetes.io/aws-load-balancer-target-group-attributes: target_health_state.unhealthy.connection_termination.enabled=true to restore "Unhealthy target connection termination" to the default value of On
4. Error!

Expected Behavior
"Unhealthy target connection termination" is restored to default value of on

Actual Behavior
Controller produces error logs

{
  "level": "error",
  "ts": "2026-03-27T10:44:15Z",
  "msg": "Reconciler error",
  "controller": "service",
  "namespace": "<redacted>",
  "name": "<redacted>",
  "reconcileID": "fb74de70-370f-4699-a8cf-73ef7109bfd3",
  "error": "operation error Elastic Load Balancing v2: ModifyTargetGroupAttributes, https response error StatusCode: 400, RequestID: 6f933ac7-86fb-4cef-87cf-744255993e14, 
InvalidConfigurationRequest: You cannot have both 'target_health_state.unhealthy.connection_termination.enabled' and 'target_health_state.unhealthy.draining_interval_seconds' enabled on a target group"
}

Regression
Not sure

Current Workarounds

ClickOps

Environment

• AWS Load Balancer controller version: v3.1.0
• Kubernetes version: v1.33.8-eks-3a10415
• Using EKS (yes/no), if so version?: Yes v1.33.8-eks-3a10415
• Using Service or Ingress: Service
• AWS region: eu-west-1

Contribution Intention (Optional)

• Yes, I'm willing to submit a PR to fix this issue
• No, I cannot work on a PR at this time

Additional Context

[zac-nixon]

Sorry, this is a sharp-edge with ELB's attribute system, where attributes that are not specified are ignored. The only way to reset this value after it's set is to find the default value, and then set it.