Pistons sometimes displace dropped items instead of pushing them

When pistons break shulker boxes. The shulker box (item form) sometimes goes above or below the piston head if the adjacent blocks are non full blocks (ex.hoppers)  instead of being broken and pushed forward.

What Should Happen:
When a piston pushes a shulker box, the shulker box should break and the item form is pushed towards where the piston is facing.

What Happens Instead:
When the shulker box is broken by the piston, the item form [sometimes] drops somewhere in the space where the piston head is. This should not happen because the shulker box is pushed in PISTON1.png is the ideal result

Edit: affects all blocks that have a chance to drop items. (Melons and pumpkins, leaves, etc)