Similary to MC-89043, but present in release 1.16.

The bug

When a piston moves a slime block players are not always launched.

How to reproduce

1. Build a slimeblock launcher as shown in the attached screenshot.
2. Walk over a corner to make the slime block push up under your feet.
   →  You will see that the player bounces inconsistently. I have not been able to discern what changes between successful and unsuccessful bounces. I have tested other entities somewhat and it seems to work for them.