Seen on mobile web, Brave browser version 1.27.109, Android 10, cannot confirm on other browsers (yet).
Following, then unfollowing a question triggers a pop-up reading:
You're no longer following this answer
Presumably this should read "you're no longer following this question", or "this post", at the very least.
The post in the image is this one, which at the time of writing does not have any answers, deleted or otherwise.
[bug] follow question answer and sorting by newest (query link) did not bring up any obvious duplicate.