Making a terrain (not an island) with a high elevation values (around 2500 meters) I discovered that the whole procedural terrain generated by the engine is heavily glitched. I uploaded several screenshots showing the borders where is obvious the difference between the custom terrain and the procedural glitched geometry.
Also I noticed that every time I load this terrain, either I close Arma or playing around the procedural map it throws an error.
Update: I uploaded the terrain if this helps to understand what happens: Ulldeter.pbo