Hello there @VNBlidion!
From what can be seen in your screenshots, and considering your setup, this is most likely a capsule positioning conflict, being triggered during the first person to third person change.
You can confirm if this is the case by running “show collision” command, which will draw all collisions outlines in game, and show you the player capsule’s status. It will also show if the grass’ collision is inactive or not.
Now, in order to resolve the problem, open your character’s blueprint, and check its capsule component. Then, adjust its Z offset in a way that the model’s feet are alligned with the bottom of the capsule.