If you have anything in your offhand slot, be it shield, dirt, diamond, or anything else, you cannot shift+right click with an empty hand to change the mode on an I/O crystal until you empty your offhand slot.

Sorry thats vanilla not me. When you right click a block the game first checks if you are holding anything in your main hand then your off hand and finally if there is nothing in your off hand it fires the right click block event. There is no simple way around this issue.

Could simply make a note of it in the block of text on the DE tablet about the I/O crystal so people aren't googling around for an hour before figuring it out :) Other than that, keep up the great work! Looking forwards to 1.10 reactor support.