Can't pickup up tower kit from the ground

[Aleksei Pankov 10]

I noticed that wehn I drop 2 opr more tower kits on the ground at the same place then I cannot pick them up. The interface look like I'm unable to perform the action: I see the name of the item at the ground, but there is no option to take it like I would cary something in my hand while not having space in the inventory. Also I don't see the kits on the ground when press TAB. Maybe this bug is due to the slightly hilly terrain.. Didn't check it on different surfaces, but checked it in two different places on the same meadow.

Like this I've already lost 4 kits in one place, trying to markup the base.

[Aleksei Pankov 10]

An update for this issue:

It's not only the tower kits, but also other objects. There is a slight slope at this place and as I understand, if axis of an object goes down under the ground mesh, the object cannot be picked up any more and are not visible at the ground when you press TAB.
Never stumbled upon this problem before on the hilly terrains, so just in case, here is the coordinate of this specific place:

Edited February 11 by Aleksei Pankov