AWS Route 53 Subdomain works intermittently

I have some strange problem with AWS Route 53 subdomain.

My main domain points to an AWS EC2 instance. I created another EC2 instance to host my dev environment. I want to access my test instance from a subdomain.

To do that, I created A records with my elastic EC2 test instance with 1day TTL.

The really strange thing is that sometimes it works, sometimes it doesn't. Just checkout the global propagation state of my subdomain and refresh the page (without cache) to see it changes every second.

What am I missing ?