Ah you seem to have an pretty old version of A6.

A5 mode means the renderer for weak 3d hardware is selected. It still supports the metal flag - the A6 renderer doesn't. There you should do some proper metal effect using shaders.

you can set d3d_transform to 0 to force A5 mode, but I cannot recommend it.
You should update your version anyway. But newer versions don't contain A5 mode anymore (it is not needed anymore nowadays).