Animated AVIF inputs return only one frame

[SuspiciousDuck]

In Discord, I attempted to embed animated AVIF images. Although one clip did successfully embed, I tried embedding 2 other clips and the preview embeds are just the first frame of the animated AVIF file. My process of creating these AVIF files were first encoding them in SVT-AV1/AOM, and then muxing them into an .avif file using FFmpeg (using stream copy).
Here are the clips I tested:
https://buzzheavier.com/5hj21lsw7di7 (successfully embeds)
https://buzzheavier.com/xuo5ewz7a2xv (has the bug, preview only has one frame)
demonstration.webm (what it looks like in discord)