DebugWriteInput doesn't work with relative paths like /debug/debug.txt. It will put it next to mp3tag when just doing DebugWriteInput “debug.txt”, but won’t travel on folder to put a file.
Using debug "on" "/debug/debug.txt does put a file in a new folder (only when it exists).
This is not a bug, but a limitation of the feature. I'm currently not planning in adding support for relative file paths to the debug feature. Please simply use a absolute path.