This is a Jetpack tiled gallery – however there is a bug: the gallery should link to the media files, but it only links to a smaller version of it. Due to this problem also captions may not be visible any longer on PhotoSwipe as the image name in the link is also used to get the caption from the database, which needs the original name without size parameter.
Lightbox with PhotoSwipe 3.2.8 introduced a mitigation for this bug which tries to remove the size parameters in image links. This can be disabled if it causes any problems.
Also see https://github.com/Automattic/jetpack/issues/16940
A new problem with captions in JetPack tiled galleries was discovered with later versions and fixed with PhotoSwipe 5.2.6.
