Nominatim DNS misconfigured?

I'm having trouble resolving nominatim.openstreetmap.org on one of my servers.

> nslookup nominatim.openstreetmap.org
Server:         127.0.0.53
Address:        127.0.0.53#53

** server can't find nominatim.openstreetmap.org: SERVFAIL

Resolving with another DNS server works:

> nslookup nominatim.openstreetmap.org 1.1.1.1
Server:         1.1.1.1
Address:        1.1.1.1#53

Non-authoritative answer:
nominatim.openstreetmap.org     canonical name = nominatim.geo.openstreetmap.org.
nominatim.geo.openstreetmap.org canonical name = amsterdam.nominatim.openstreetmap.org.
Name:   amsterdam.nominatim.openstreetmap.org
Address: 130.117.76.9

I already contacted support of the DNS server that my server uses by default and they replied, saying the following:

Our investigation shows that it may depend how their domain is being queried: if geo.openstreetmap.org is resolved first the misconfigured records [1] are being cached and will make any other related queries to fail.

It works if nominatim.geo.openstreetmap.org is resolved first and the (almost) correct records being cached for further queries. [2]

[1] https://mxtoolbox.com/SuperTool.aspx?action=dns%3ageo.openstreetmap.org&run=toolpage
[2] https://mxtoolbox.com/SuperTool.aspx?action=dns%3anominatim.geo.openstreetmap.org&run=toolpage

As one can see on the mxtoolbox site, it reports quite a few warnings for the DNS config of these domains and especially one error for geo.openstreetmap.org.

I'm not sure if I should have rather created an issue on GitHub or if this is the place to report potential bugs...