Huh. There is a file in the repair room that is pretty blatant about what to do there, as least to me.
I think it's sorta obvious after you get the materials.
In hindsight, i was probably expecting most players to get the mandatory item before reaching that point with the PRMI room in Tower of Light, but of course it would be common with the non linear nature of the game haha
Maybe i should change that in an update. It can be really misleading now that you mentioned it.