Two of three endpoints (for api64) are unreachable?

[AndreKR]

These are the servers I get for api64.ipify.org:

# dig aaaa api64.ipify.org @8.8.8.8

[...]

;; ANSWER SECTION:
api64.ipify.org.        300     IN      AAAA    2607:f2d8:1:3c::3
api64.ipify.org.        300     IN      AAAA    2607:f2d8:4010:51::5
api64.ipify.org.        300     IN      AAAA    2607:f2d8:2010:2::2

[...]

Two of those don't work for me (tried from two different servers):

# curl -6 -v https://api64.ipify.org/
*   Trying 2607:f2d8:4010:51::5...

# curl -6 -v https://api64.ipify.org/
*   Trying 2607:f2d8:2010:2::2...

One works:

# curl -6 -v https://api64.ipify.org/
*   Trying 2607:f2d8:1:3c::3...
* Connected to api64.ipify.org (2607:f2d8:1:3c::3) port 443 (#0)
[...]