Cannot place upwards / downwards facing pistons and commands blocks near world end

When near the end of the world (30,000,000 blocks) you cannot place pistons and command blocks upwards or downwards at certain x and z values in a chunk. Instead they will always turn sideways.

Affected coordinates in a chunk:

• 1
• 5
• 9
• 13

The screenshot shows the result of trying to place pistons facing upwards. The lapis lazuli blocks mark the 0,0 corner; the redstone blocks mark the 15,15 corner.