Steps to reproduce:
Have parrots on your shoulders.
Try to riptide anywhere (preferably while raining).
Observed results:
The riptide stops instantly as if you hit a mob/entity.
This probably happens because the riptide trident hitbox is colliding with the parrot's hitbox even though they are on your shoulders (the parrots don't get hurt). If you riptide up you still get stopped, but you still take fall damage even though you never left the ground.
Taking fall damage in this situation even though you don't move is probably related to the general problems with fall damage desyncing. See especially MCPE-126454.