What's happening here?

[Mana]

The block looks like it is hovering from this side.

 

[Melange]

Yep. Not a mechanical issue, but it does look strange.

Ever kill a rabbit or chicken and have to follow its carcass because it didn't like to be where it was killed?

Immersion breaking? I find humor in it. 

 

[Crater Creator]

I've noticed this with more complex blocks, like loot containers and cardboard boxes, mostly when shining a torch or other first person light on them. It's as if the shadow isn't cast by the geometry you see, but instead by a slightly different, probably lower poly invisible mesh. I assume it's a way to cut corners when rendering shadows, for the sake of performance, but I don't know.

 

[Syphon583]

That is odd. You'll see this a lot when placing blocks directly on terrain blocks, but clearly this isn't the case. I would also normally consider whether the blocks beneath aren't full blocks, but judging by the fact that all of the other surrounding blocks are sitting flush, that doesn't seem to be the case either. Just a weird rendering issue would be my guess.