Well those are dumb problems but sniffing UA doesn't really fix them. You'll still have clients suddenly broken.
....what the heck is an animated WebP
....what the heck is an animated WebP
what the heck is an animated WebP
A drop in improvement for animated GIF: https://developers.google.com/speed/webp/faq#why_should_i_us...It does clarify that it's at least not quite WebM, but it doesn't explain how far away it is.