Error: Leave site? Changes may not be saved

I don’t know if this error is still a known issue, but apparently it is still happening with my sites.

The issue only seems to happen when trying to do a preview of a page that has been updated. It does not appear to effect posts.

After updating a page, I get an error when trying to do a page preview that says, “Leave site? Changes may not be saved.”

Actually, it does do the page update, but you still have to choose “Leave”. It will show the updated page anyway.

Most people that have posted this error say that it does not do the update, but on my sites it does, but I still have to choose “Leave” when trying to do the page preview.

It does not matter what plugins are enabled or disabled or if you are in view mode or text mode. Some people thought it only effected sites with Woo Commerce plugins. I do not have Woo Commerce installed on any of my sites. It seems to be a WordPress core issue.

I read somewhere when I was googling this error that it was an error in the WordPress core and it was supposed to be fixed in WordPress 5.6.1 which is what I have, but apparently it hasn’t been fixed.

I was just wondering if anyone is still having this issue and if it will be fixed in the next version.