Servfail which server,

sometimes I do not get an ip address for one of my domains.
I really have the feeling, but I can't prove this, that at that moment the nameserver of my hosting company isn't responding as expected.
I checked my pi-hole to see if I could find anything, and what I do can find is SERVFAIL.

which I assume is not good.
But I would like to have some additional information, like what server or something.
is it or some other server?
If I have this information I can complain with solid prove that they have an issue.

Is this at all possible?

"BOGUS" refused by upstream" indicates a problem with the dnssec authentication for that domain.

that could be,
but this hosting provider does not support dnssec.

as you can see, "INSECURE" when it works.
but "BOGUS" always means an issue with the nameserver?
because that would be valid proof I think.

BOGUS means a certificate was found, but it is not valid, so the domain is determined to be BOGUS.

If a good certificate is found, that results in SECURE. If no certificate is found, the result is INSECURE.