I can't reliably reproduce this bug. 

This only happens with connections with passwords/credentials. localhost succeeds. I'm thinking there's a race condition in our connection loading logic. It could be something with migrations - it's worth seeing if this happens after the extension auto updated.

See the linked node ticket. This appears to be caused by a dns issue on windows with certain node versions https://github.com/nodejs/node/issues/62326 

There might be a seperate race condition issue with loading secrets, I once had connections fail when opening VSCode after fully closing it on my mac. When it opened I opened the extension and tried to connect to a cluster. It fails consistently with Unable to connect: querySrv ECONNREFUSED mongodb.tcp.cluster0.omittted.mongodb-dev.net
This happens to all connections with credentials.

Opening a new VSCode window, all of the connections work in the new window. They still don't work in the original window.