It looks like the DNS server 139.178.70.122 (m1.ntppool.org)
is in trouble.
$ dig +tcp www.mapper.ntppool.org @m1.ntppool.org.
;; Connection to 139.178.70.122#53(139.178.70.122) for www.mapper.ntppool.org failed: connection refused.
$
With UDP it times out.