The issue is not present in the CPM editor (both in-game and web versions), but occurs exclusively when opening .cpmproject files in Blockbench.
Example File
comproject.zip
Blockbench
CJK.cpmproject
Emoji.cpmproject
Encoding Error
The config.json is natively saved in UTF-8, but the CPM Blockbench plugin incorrectly reads it as Windows-1252 / ISO-8859-1.
I tried to fix this myself, but the underlying issue turned out to be quite complicated.
Also, why is the CustomPlayerModels-EditorWeb symlink required during the plugin build? (ln -s ./Web ./CustomPlayerModels-EditorWeb)