The RF API that's included is the BuildCraft port which is incompatible with the official port, leading to "method not found" crashes (e.g.SleepyTrousers/EnderIO-1.5-1.12#3428 ). Would be nice to use the official 1.8 port instead, it only needs one tiny change to work on 1.9.

Yes, this problem also causes a conflict with RFTools

Fixed!