What steps will reproduce the problem?
1. Press the button to clear all markers in a non-english WoW client.
What is the expected output? What do you see instead?
What version of the product are you using?
Do you have an error log of what happened?
Please provide any additional information below.
"/clearworldmarker all" only works in english WoW clients. I somewhere read that "all" has to match the value of the global variable ALL and indeed in the german client it works if I use "/clearworldmarker alle" (value of ALL is "Alle"). But it also works if I just use "/clearworldmarker 0", so I assume that would be the easier solution for you.