Slime block not able to block fall damage when timed perfectly

In my Redstone world, I was testing if a line of observers give the same speed as a falling player. Then I tested it in create mode and it did just fine, but in adventure, things gone wrong. Even with the slime block below me I took fall damage. What was intresting to me is that I still bounced. I shared a screen recording and a world download for this glitch.

I hope this glitch gets solved soon!