On my server I have, for example, in an interface to an Industrialcraft2 macerator, 2 recipes for crushed iron ore - one for gravel iron ore and one for normal iron ore. Now, the crafting system seems to completely ignore the crafting pattern in the interface that is more to the right of the screen. In my case this would be gravel ore -> crushed iron ore, so whenever the system would need to use that, it tells me that not enough resources are available. I don't think this is intended behaviour, so I'll report it here as a bug.

Okay, as it turns out, I just used AE2 incorrectly.
I forgot that I need to configure different interfaces with different priorities in order to make it work properly - now that I've done that, the system can use both recipes correctly. Sorry for bothering, I'm going to close the issue with this comment.