I have the same issue with grant and have tried waiting for several days and nothing seems to work.
I also have this issue with Ranger Grant. My only dialogue is "goodbye" and he responds(goodbye) in some weird synthesized voice. Can a patch somehow fix this? I've done traveling in the mean time, but the situation with Grant is always the same. This interaction is key for quests "you'll know it when it happens" and "for the republic: part 2", both of which say go see Grant. I guess I'll wait and see if it changes.