Hoppers not placing items into dispensor

On our realms server I created a dropper elevator, however seemingly for no reason, the final hopper wont place items into the dropper. This happens for all of them. Strangely, its passes 3 or so items through whenever a block update is applied, so I placed a piston on a clock to update the block and it works fine, but creates a lot of unnecessary lag.

 

There is no block powering the hopper like someone suggested, all redstone is inactive. Only one of them are on a chunk border, but all 3 of the hoppers are misbehaving in this way.