AWS: can't duplicate DNS settings for an existant domain

I have a domain with an A record of dualstack.prod-clients-alb-1234567890.us-east-1.elb.amazonaws.com. I'm trying to have another domain point to that same server and am unable to do so. When I do so I get the following error:

Bad request.
(InvalidChangeBatch 400: ARRDATAIllegalIPv4Address (Value is not a valid IPv4 address) encountered with 'dualstack.prod-clients-alb-1234567890.us-east-1.elb.amazonaws.com.'')

If it must be set to an IPv4 address than how did my other domain get an A record of dualstack.prod-clients-alb-1234567890.us-east-1.elb.amazonaws.com.?

I also tried checking the Alias button and selecting "Alias to Network Load Balancer" for the endpoint and setting the region to us-east-1 but I'm not seeing nay resources for the network load balancer. Maybe I need to be using a different endpoint? If so can I figure out which one I would need to use from the A record of the other domain?

(both domains are going to be hosted on the same machine / ECS instance so they should have the same settings it seems to me...)

Use A and ALIAS and if you don't see your ALB in the drop-down menu you can write / paste the dualstack...com. name there. The drop-down only shows ALBs from the same account that are not already used but it should be perfectly possible to create a new A / ALIAS for an already existing record. It just doesn't show up in the menu.

FYI - Simple A record requires an IP address, e.g. 192.0.2.123, while A / ALIAS record requires a domain name of one of the supported services, e.g. ALB, that Route53 resolves for you to an IP address.

Hope that helps :)