While approaching slabs, your character jumps rather than just walking up the slabs like stairs.

In this situation, it's only just a small fraction of the time you would jump rather walk up the slabs like stairs. I feel like this might be a bug, but I wanted to address this to you, the developer, and see if I'm reporting correctly.

This "bug" gets rather annoying when using slabs as stairs for decoration in front of doors. I attached a pic to give just an example of the situation.

Also too, this happens on creative just as well on survival.

Thanks Mojang

EDIT: This is still affecting versions all the way up to 0.9.4. It only happens a few percentage of the time. Seems like it happens when a full block is behind a slab