Top half slabs duplicate when attached to slime block shifting floor

When attached laterally to a quick pulsed shifting floor pushing north then south made from slime blocks, dark oak top half slabs duplicate and accumulate at the south end of the dark oak top half slabs attached to the slime blocks.

The duplicated dark oak top half slabs do not move as part of the shifting floor, can be stood upon, can be destroyed, but do not yield an inventory item when destroyed.

Also, during the shifting floor transition, the top half slabs appear to temporarily become three quarter blocks.