When editing a post and picking an image from the WP media library, if you open the modal to pick and image from the GPI media library, then the confirmation button should both insert the image into the WP media library and insert the image into the post. However the last part is not working anymore. The image is inserted into the WP media library, but not added to the post.

Note that on the post editor currently the button says "Insert into WP Media". This seems to be a separate regression, as on the "Media > Add New" page the button says "Insert into WP Media & Post". Looks like at some point the buttons were swapped. It could be that only the label is affected by it.

Probably by the technique that is used to add the image to the post doesn't work for the Gutenberg editor.