The host (assuming the same host) is responding with a different website when accessed via IPv4 vs IPv6.

  $ curl -4s http://kairos.xyz/ | grep title
      <title>Kairos</title>

  $ curl -6s http://kairos.xyz/ | grep title
  <title>Welcome to nginx on Debian!</title>

  $ host kairos.xyz
  kairos.xyz has address 107.161.29.121
  kairos.xyz has IPv6 address 2604:180:0:a54::24d9