The problem is broader than only user reviews with spoilers.
User reviews have a permalink that points to nowhere.
This is the case with many (or even all) user reviews on many (or even all) movies.
An example: movie Daddy's Girl https://www.imdb.com/title/tt1662546 has 2 user reviews. Both have a wrong Permalink, yielding an error message.
I tried many other movies, and the problem is similar everywhere.
I can t find my review which was here: