@welshpixie @futzle @cefiar 🤔 Hmm. That's odd...I was expecting an option to "use Dynadot DNS" or something. I'd say it's safe to hit save on that though - either it'll go through and things will be fine, or it won't and nothing will change.
As a backup, do you have access to a Namecheap account? I noticed the other domains are using that for their nameservers.