Newsletter editor/builder is kind of buggy at the moment.

I get that quite a lot. Especially when I use Brave Browser. How is it buggy for you?

I talked to support about it, and they were helpful. Recommended incognito on the browser, but I usually just switch to Firefox when I want to embed a link. I find that 'Preview' often hangs when I'm writing a post, and I often don't get the 'warning' that my post is getting too big. But these are minor issues, to be honest.