WP 5.9 Media Library Overlay Caption Changes Are Not Updated In Gallery

[linux4me2]

Steps to reproduce the issue:

• Add a new Gallery Block to a post or page in WP 5.9.
• Add at least one image, without a caption, to the gallery.
• Using List View, select the Gallery.
• Click the Media Library button to display the Media Library Overlay.
• Click the Edit Gallery link.
• Click an image to select it.
• Add a caption to the image.
• Click the Update Gallery button to save the changes.

In WP 5.9, the added/updated caption is not added to the image in the Gallery Block.

It's possible to add the caption to the image in the Gallery Block directly, but it would be nice to be able to add/update captions in the Media Overlay and have them updated for the image in the Gallery Block.

[glendaviesnz]

Thanks for reporting this @linux4me2. Because the Gallery block is now using nested Image blocks it is mimicking the current behaviour of Image blocks, which is to include the alt text and caption from the media library the first time the Image is selected, but for additional edits, the alt text or caption in the block becomes the source of truth so won't be overwritten.

This is intended behaviour, and there is some background discussion about this decision ​here, ​here, and here.

[linux4me2]

Thanks for the explanation and the links @glendaviesnz. I understand now. It makes perfect sense.