Trying to delete a subclass entry of a QoS parent class (for example, "TOS Bit matches") by hitting the trash can icon next to it does not delete that item. The web page reloads with the same contents.
I noticed a missing translation in qos.cgi and it happens to fit this bug description. I think this patch should fix it: https://patchwork.ipfire.org/patch/4536/
https://git.ipfire.org/?p=ipfire-2.x.git;a=commit;h=fc81e493b14d545893856d5bcba11d538a8ae16c Thank you very much! :-)
This was released with Core Update 160. https://blog.ipfire.org/post/ipfire-2-27-core-update-160-released