For few weeks now, I encounter issues using 1.1.1.1 or 1.0.0.1 as my DNS server.
Everything actually works well, but after a random time, all my DNS requests timeout and I can’t ping these IPs. Then, after a few tries, it works again.
Here a trace route capture during the problem. I don’t know from where the problem comes from.
For this particular trace it would appear as if the issue was with your own ISP. The first hops already time out and the third hop is eventually reachable only after a second.
I must add that disconnect and reconnect the WiFi connection on which these DNS servers are configured also resolves this issue. But, it happens so often that it is not good workaround