Custom ordering stopped working

Good day, to you all.
After a while custom ordering stopped working on a page. I checked everything, and all seems to be fine, but no luck. Anything wrong here?
items: @self.children
by: default
- web
- logo
- graphic_design

I tested, all works as usual. Make sure cache is disabled or cleared when you test.

Hi, flaviocopes. Cleared. Did already everything. I’m just confused. Have no idea what is happening.

What may change the behaviour of frontmatter?

I think I found a bug. If the Slug is defined, the custom order is not working, if the Slug is note defined, then the custom order is working.