When I set zoom on an orthographic camera to anything above 1 I get a strange black border on the bottom of the screen.
I suspect that this might be some sort of culling problem. I use a viewport to control the game resolution, and no matter the size the borders are there.
The camera is set on a direction (-1,-1,-1) basicaly isometric. Also it is positioned well above to origin at (1113,1113,-1113). Far plane at 7777 near at 0.00001f. The ground plane is at 0,0,0 laying in the xz axis, with an other plane on top of it sligtly off to the left and with a 45 degrees on its axis to face the camera.
Here is an image of the problem:
Posting code wont really help here since I only use defaults almost everywhere, but if you need it just tell.