Some name servers, but not all, are unable to resolve

But even those which are ordinarily unable to resolve seem to be able to get answers with dig if
the +trace option is used.

For example, this web site:

offers a browser interface to dig. If you use their
localhost as the server and query for an A record, but
don't specify "trace", then the unhappy result is
"connection timed out; no servers could be reached", but if
you do specify "trace" then you get 6 answers.

Similarly from the command line:

dig # times out
dig +trace # OK

But other name servers handle it fine (and dig works
even without +trace):

dig # OK
dig # also OK

The only shortcoming I see with the setup is
that the whois record only has 1 name server
( listed.

For comparison,, has similar characteristics
(though the whois record lists both and, but it doesn't result in the same failures
I'm seeing for

Any and all help appreciated.