[atlas] DNS issue with Atlas or with the ISP?

RIPE Atlas Web site displays a lot of "undefined" for the tests in AS
3125. See for instance
<https://atlas.ripe.net/measurements/22766270/#!probes> or
<https://atlas.ripe.net/measurements/22766942/#!probes> But the DNS
resolution from this AS seems to work.

Checking the raw results in JSON, I see that we have a lot of failures
on one IPv6 resolver:

        "dst_name": "fe80::a63e:51ff:fe77:e26",
        "error": {
          "socket": "connect failed Invalid argument"
        },

We do not see such IPv6 problem in other AS (see for instance
<https://atlas.ripe.net/measurements/22766995#!probes>)

I assume that the "connect failed Invalid argument" is the fault of
the ISP, which advertises a wrong DNS resolver? Or is the Atlas probe
unable to query link-local addresses for DNS resolution? 

Even if it is so, is it a good idea for the Atlas Web site to display
"undefined" where the raw results show that other resolvers worked?