Means they see a lack of information in what the MEB provided. Usually it means they think there is good reason to think one of your other conditions is also unfit and want to see the question explored properly. I have seen this when the commander talks about a condition being a problem but the docs did almost no work up on it. Sometimes it ends up becoming unfit, sometimes it doesn't. It is possible that the workup for the referred conditions doesn't appropriately answer the fitness question well enough, I have heard of the MEB stuff being pretty sloppy and the PEB just saying nope, do your job, but this scenario seems to happen less now.
