Update:
This problem is still happening for me, but the error message seems to have been changed. It now has appended: "(Remember it could be a trashed item)". So I presume, someone from the team is following this forum?
I'm still having the problem, please see the error message and 3 screenshots from my category manager for live, trashed and archived items:
https://www.automatem.co.nz/images/issues/jseblod/jseblodcatmanager.png
https://www.automatem.co.nz/images/issues/jseblod/jseblodcatmanagertrashed.png
https://www.automatem.co.nz/images/issues/jseblod/jseblodcatmanagerarchived.png
Does anyone else still have this problem?