Lachlan can be seen walking around the ship lifting heavy things, only occasionally because someone asks him to. As he does, you can see him sometimes shale his head in an odd way. If asked, he says he always thinks better while working out, and there was something that the Celestial/Proxy/Avatar Lady said in passing about the Oni that he thinks might have been important and he is trying to knock it loose in his head.
And because it probably happens often, when someone asks if Lachlan wants them to hit him in the head to see if it helps knock the memory loose, he will agree, but only if they let him hit them in the head too...