Subdomain redirected to root


I’m having trouble to figure out why my subdomain is redirected to root.

I have 3 dns records:

  1. A - root - ip address of some cms service
  2. CNAME - www - root
  3. CNAME - subdomain - heroku dns (different site than a record)

When I put subdomain[dot]root to my browser i end up at www[dot]root[dot]io.
Browser is showing 2 redirects: First to root[dot]io, second to www[dot]root[dot]io.

I don’t understand why is not pointing to my heroku application.

Do you guys have any ideas?