Hey, I'm also facing a similar issue.
One month back, I bought an expired domain (clean anchor profile and history) with a few pages indexed. After that, when I set up the theme (importing demo content) many of the dummy pages also got indexed).
Post theme setup, I published three posts, each of which got indexed on google and started ranking on the 3rd - 5th page within a week.
After 4 - 5 days, the website suddenly disappeared from search results for most keywords ( google dance, maybe?).
Post that, I published a few more posts (4000+ word detailed post every day), and none of them are indexed on google.
Also, the pages indexed before are not visible on doing the keyword search + domain name on google.
Even google console behaves strangely, with a submitted sitemap showing the old post count and not getting updated.
Not able to understand the issue. Could someone please help?