Sand, gravel, and concrete powder will drop as an item on certain blocks that it shouldn't such as pistons.

Sand and gravel are dropped when landed on pistons (both types), glass, ice, leaves (all types) and stairs (all types). This should not happen because in Minecraft pc this does not occur because items such as torch, pressure plate, chest among others is for this to happen naturally the opposite of the first items quoted.
This bug affects not only the piston but other items that normally should not happen such a bug.
Samsung Galaxy Tab E SM-T560

Concrete power has the same issue for: glass, ice, leaves and stairs