Walking Diagonally Across Farmland

Hello!
Bit confused here. 
If I walk across the 2x1 hole separating Farmland from my Cut Sandstone, I do not fall in the hole. But if I walk straight across the gap, I do fall. walking/sprinting doesn't matter.

 

Please refer to screenshot for an example. The lever is pointing west if that helps.
all of the farmland has hoppers under it.

 

The lever has a block of red concrete under it with a dot of redstone on top for power transfer.

the shulker box has a hopper feeding into it.