SMP Duplication Glitch with hoppers on chunk borders

Expected:
Two or more hoppers connected in an infinite loop, should cause a few items to be constantly moved from hopper to hopper. Regardless of their position relative to chunks.

What happened:
About 12 iron blocks were cycling around in a hopper loop. These hoppers were far from other hoppers and were covered with opaque blocks. After a few hours a full stack of Iron blocks was in one of the hoppers.

Replicate:
Place 4 hoppers at the border cross of 4 chunks, with the spouts facing in a clockwise direction. Place 2-3 items in each hopper. Wait about an hour. Check all the hoppers for extra items.