I wanted to relay a personal story related to the original post.
I moved to a new city about a year and a half ago. I left an excellent club and joined an equally excellent club in my new city. Both clubs are Aikikai, but the new club is under a different Shihan, so there are some style differences.
My new Sensei and fellow students, recognized my rank at the time (ikkyu) which was an honor considering the circumstances, which I will explain. Differences in training method and technique details were enough to really throw me off. I felt fairly comfortable and confident in my old dojo but now found myself making mistakes and even fouling up some of the fairly basic dojo etiquette.
My point is that it is not easy to change from one dojo to another, and your friend the Orange belt is not having an easy time. He needs understanding training partners and senior students to get through the transition. Would it be better to retest for his current rank? As others have pointed out, that is for Sensei to decide. Sensei is most likely taking into account all that this student is going through. Perhaps in time things will get easier for him.