I don't know if anyone else is experiencing this, every planet I have visited so far my vehicles clip through the surface to fall to the center of the planets.
For Kerbin, when I drive to the top of a hill my vehicle will just fall into the planet. https://imgur.com/a/U8sXxON.
On Moho, Jeb fell through the surface just walking and is now on a intergalactic trajectory. https://imgur.com/7rInUqp, https://imgur.com/oWMG62U, https://imgur.com/CrTjmI5
On the Mun, if I leave a ship there and return to it the ship will clip through the surface.