The Bug:

When pathfinding, Sniffers sometimes have a hard time jumping up a block if a non-full block is beneath them, such as Pink Petals, Carpets, or even something with no collision like Torches.

A video of this behavior can also be seen here:
SnifferJumpUp.mp4

Note that this isn't just about its Hitbox size, as Ravagers do not have this issue.

How to Reproduce:

1. Summon a Sniffer and put it in a situation where it needs to jump up a block with a non-full block below it. 
2. Notice how it will get stuck and not be able to jump up
3. Repeat this proccess without the non-full blocks; the Sniffer with pathfind like normal.