POST quickedit/metadata 404 (Not Found)

Problem/Motivation

Trying to add a block with a picture in the text editor returns the error in title and does not add the picture.

Steps to reproduce

Go to a layout builder and try to add a block that contains a WYSIWYG text field.
Select the media/image you want to add.
Click Save.
The image of the text is not added.
In the console you can see an error "POST quickedit/metadata 404 (Not Found)".