Multiple cameras not working correctly on iPad Air

I'm having a bit of trouble layering the image from one camera over another. Everything works fine in the editor:

When i run it on the iPad Air i keep getting graphical glitches like in the bottom left of this picture:

my cameras are set up like this: Main camera, depth: -1, clear flags: sky box, culling mask: everything

Second camera, depth: 0, clear flags: depth only, culling mask: test

the capsule is on the "test" layer the second camera and the capsule are far above the main camera and the other objects

both cameras have clipping planes of 0.3(near), 1000(far)

Any advice would be much appreciated