@zenkamal @a_5mith This sounds like it's due the new way we store post bookmarks.
Before, we stored the pid (e.g. 2341)
Now, we store the post index (e.g. 5)
The bookmark only updates if the current post # is > than the bookmarked post #
Unfortunately, 5 will never be greater than 2341, so the bookmark never goes away.
The old bookmark is basically trying to load the 2341th post in the topic, which doesn't exist. You can clear the bookmark by clicking the "x" at the top right of the notification alert, then that topic should be fixed.