Random Falling Damage, No Elytra, "Falling" through full and partial blocks

While attempting to make a mob farm I ran into an issue building. While placing the slabs for the roof so no mobs would spawn on the roof, while allowing no light to reach the blocks underneath I kept dying to random fall damage. I had found that others also have had this issue but only with partial blocks. So I returned to my build with full blocks to block out the sun. The video shows what happened next. But the random fall damage seems to be affecting more than just the Elytra. I'm now not even able to go down stairs, walk across my farm. Any and all partial blocks have become a near instant death.