If anyone knows where I should head to for help, please do tell me.
Currently the issue is, I've DLed the latest version of RotaryCraft and it's DragonAPI.
And also UE's Core, ICBM and CalclaviaCore.
And now my MineCraft gives me this error. But I can't run either set of mods by removing any of the "duplicate" files. So, any suggestions?