I tried to see if this rare bug was brought up before, but I didn't find anything.

The following profiles:

... have top posts like this:

missing title

A missing title, and the link goes to, for example:

... which is 404 page not found, but the post is alive here:

All those posts were migrated as @Arulkumar noted in a comment here, so the issue seems to be with the migration.