I believe this issue is caused by the way WPML add’s it’s language switcher to the taxonomy edit page.
Instead of appending a ‘tr’ element, it clones the last ‘tr’ elmeent in the table.
In your case, this last element is a WYSIWYG field.
In cloning this field, WPML is causing ACF to initialize a WYSIWYG field on an element which does not exist.
Can you please contact WPML and ask them to look into this issue?
It would solve the problem completely if they added a standard ‘tr’ element, not cloning the last element.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users