There is no fix for this because at least the AGS Industrial p3d objects cannot be read by WrpTool. You just have to live with the object icons instead of the real p3d shapes.
WRP-tool gives you an error, but in the game the buildings are there. So it is possible to place AGS-Objects with WRP-tool.
But there is still an error: I don't know if others have this problem too, but in my island, the AGS-builidngs (and other inofficial addons like some of JörgF) sometimes do not fit to ground and sometimes they do. I didn't find out on what this depends.
One way would be to place them ingame with the mission editor, giving the obj a name, and then making a repeating radio alpha-bravo-charlie trigger set to move the object N meters in XYZ. Radio Delta could be a trigger that hintc's a getpos of that object.
With this info, you could manually place the object in WRPtool based off of the coords you pulled from in game. Using the -window switch on OFP can also help so you can see ingame for reference on placing the objects.
nono my friend, thatsnot the point, i dont even see the buildings in game. I placed them in WRPtool but dont appear in OFP. Instead of the buildings i got little circkels like trees on the map and nothing visiuable