unsaved content and autosave

I have used wordpress for years. My sites are now hosted at the reputable dreamhosts.com (no complaints).

After the upgrade from WordPress 5.5.3 to 5.6, I noticed a bug (or a feature?)

1) on https://tanbinvest.dreamhosters.com/wp-admin/post.php?post=19234&action=edit I remove the last punctuation in the first paragraph

2) without saving I click on the All_Posts link in the menu.
2a) First time I get the pop-up prompt/warning about unsaved edits. So I stayed on the editor page.
2b) Second time I get the same pop-up. Again, I didn’t navigate away.
2c) The third time I click on All_Posts, I was able to navigate away without saving my edit. There’s no prompt this time. I guess this time my unsaved edit was saved in some local cache (autosave?) Maybe the autosave kicked in and confused the alert logic as if the user manually saved the edit?

3) when I return to https://tanbinvest.dreamhosters.com/wp-admin/post.php?post=19234&action=edit, I see the banner above my editor warning “The backup of this post in your browser is different from the version below.”

Sometimes, I don’t even see the banner warning, and my unsaved edit is lost.

The correct behavior is — regardless of the local cache, every time the system should notice the unsaved edit, and should always, reliably prompt the user to either save or discard the edits. I believe this is the behavior I saw for a few years.