When returning from the nether, the compass does not point to the spawn point.
It points in a different direction.

What I expected to happen was for the compass to point to the original spawn upon returning from the nether.

What really happened was that the compass pointed in a different direction when I came back from the nether, (according to my estimations, it may be pointing to z = 0 and x = 0, but that is not confirmed).

The first screenshot shows where the compass is pointing after returning from the nether, the second screenshot shows how the compass is supposed to point, to the original spawn point, note the difference in both screenshots.

Also, the problem is fixed if you restart Minecraft.