Your name servers are taking too long to respond to Google's resolvers, which will return a SERVFAIL if they are not able to fully resolve (including looking up addresses for the name servers themselves) a domain name within 5 seconds.
"Comment": "Response from ns11.dnsecure.biz.(210.48.153.241); 3774ms resolution time exceeds 2 seconds; some clients may time out.",
"Comment": "Response from ns12.dnsecure.biz.(210.48.153.240); 3786ms resolution time exceeds 2 seconds; some clients may time out.",
I would strongly recommend that you set up additional secondary nameservers for your domain (
dns.he.net offers very good coverage, and is free) - you would need to allow the
he.net nameserver IP (216.218.130.2) permission to AXFR zone transfer your domains (See
https://forums.he.net/index.php?topic=1006.0 and elsewhere at
dns.he.net for instructions about that side) and arrange for your primary name server to send NOTIFY when you make changes.
Then you would need to add the additional
he.net nameservers to your domain registration in addition to ns*.
compraensanjuan.com.
This expanded nameserver configuration will improve the reliability (by adding name servers on a second network AS number) and reduce resolution delays for your domain not only through Google Public DNS, but worldwide through any resolver.