Hey there,
It seems that if you add the images from the Joomla TinyMCE editor, it doesn't add the leading slash on the image link as shown in the screenshot.
https://monosnap.com/file/8RBeOavayFzkXNeXmETyUA1MqkgdWg
So when you edit this article through the EasyArticles composer page, the image showed broken and we are not sure why this will cause the invalid token yet.
For now, we had added the leading slash on the images' link via the EasyArticles composer page and save it. You should be able to update this article via the EasyArticles composer page now.