In DS9 S3E9 "Defiant", Tom Riker (Will Riker's transporter-accident-created twin from TNG S6E24 "Second Chances") comes to DS9 disguised as Will. When he (still in disguise) bumps into Miles O'Brien, the chief greets him warmly, but Riker says, "I have nothing to say to you, O'Brien. You know why."
I have always wondered what this was about. Obviously, if you're impersonating someone whom you don't know very well (Tom Riker having spent eight years entirely alone), you don't want to interact with people well known to the person you're impersonating, because they may catch you out in an inconsistency... so was this simply a way for Tom to get rid of O'Brien, to avoid an awkward situation?
If so then it was foolish on Tom's part, because if there was no dispute, the chief might start to wonder why Riker was snubbing him. So can we assume that Will Riker and the chief had had some falling out and Tom had found out (through intelligence gathering somehow)? If this is so, is it ever explained what this falling out was all about?
I know Riker and Worf had some disagreements over Deanna Troi (either in the "real" universe or some quantum alternative). But I don't remember any problem between the chief and Riker from the TNG series or the movies. Does anyone know?