Item frames "jumping"

At very large distances away from spawn (2,000,000 blocks is where I noticed it), item frames "jump" when you move, and at certain angles the background disappears into the block it is mounted on.

Possibly unrelated, but MCedit becomes unaligned between actual position and appearance of blocks at these distances.

Note: In image, the item frame on the right is mounted on a non-opaque stair block.