When I placed a Sniffer in a frozen ocean biome (on a layer of ice), I noticed two things:
The Sniffer's Walking animation does not play while it's walking on ice.
Sometimes, the legs would go in a mid-walking position and the head would just disappear for a few seconds, as seen in the attachment.
Hope this helps!
1. Confirmed
[media]2. Dupes MC-260125