Resolved the issue when stashes are buried under watchtowers the Underground Stash will be placed ontop of the highest available watchtower "floor". I was able to resolve this by changing the line of code in the " undergroundstash.c " file from

void PlaceOnGround()
{

		vector pos = GetPosition();
		pos[1] = GetGame().**SurfaceRoadY**(pos[0], pos[2]);
		pos[1] = pos[1] + 0.22;
		SetPosition(pos);

}

to:

void PlaceOnGround()
{

		vector pos = GetPosition();
		pos[1] = GetGame().**SurfaceY**(pos[0], pos[2]);
		pos[1] = pos[1] + 0.22;
		SetPosition(pos);

}

It seems SurfaceRoadY makes the object appear ontop of other objects where SurfaceY is actually to the map.