I need a stack trace to debug this; the information provided is not enough for me to understand what the user was trying to do.

I think I fixed this recently... the issue is that "rcat" should have been "r.rcat". Several content hooks were missing "r."

Edit: Realised this is a v10 issue. I only fixed this on v11. v10 is in maintenance status so this won't get fixed in v10 without sponsorship.