Typically, if you tap on a post’s image, there is a quick animation that scales the image up from its current location on the screen until it fills the screen completely.

For some reason, sometimes when the post image is tapped on very quickly after the post is loaded, the animation is skipped.

It doesn’t seem to occur consistently, but in recording it for the GIF below, it occurred on my fourth loading of the post, each time quickly repeatedly tapping on the post image as soon as it appeared. The GIF itself consists of the third and fourth of those loadings, with the third having the normal animation and the fourth lacking it.

As the difference is harder to see at low frame rates, I tried uploading a high frame rate GIF to no avail, so if needed I can share the original video file via different means.