me and 2 others experienced the same issue, the collision / bounding boxes of the majority of the rocks cropping out of the terrain seem to be very far from perfect.
some rocks you are able to get on top of without issue, but going prone or crouching on them will show you floating due to poor collisions set on the rock "object". other rocks seem to have bad collisions for their sides, resulting in them being unable to climb when it should typically not be an issue given their height, as this case description suggests.
we found this was more problematic when we were already on top of one rock, and trying to get on to another.