Not all categories work?

I have the same problem…yet again.

The other Random Redirect worked OK with “?random=” appended to the URL, but still wouldn’t work for specific categories. This one has the same issue. I think it has something to do with attempting to use a category that has multiple child categories. I want the link to target any one post from 4 different categories. These 4 categories are under one parent category, so I figured I could use that parent category ID to redirect to posts from a variety of specific categories. But it doesn’t seem to work that way. For now I may just go back to using “?random=” because I don’t want to specify one of the child categories.