An official one. In the original Invaders run we met Iron Cross/Helmut Gruler, a German armored hero, working for his country during the Second World War because he was a patriot and out of a sense of duty, BUT very, very clearly stated to not be a Nazi and to actively dislike his country's current leadership. This was reinforced when a post-war Iron Cross was revealed to have been a member of the V-Battalion from shortly after the war all the way into the modern day, and to have actively helped them with hunting Nazi war criminals, the reason the Battalion was initially formed. 

Then in Midnight Sons Unlimited we saw WWII era Iron Cross being a proud Nazi and committing war crimes by deliberately (and with glee) targeting civilians. Invaders Now subsequently again depicted an Iron Cross happy to commit war crimes in the name of the Nazis. 

If the V-Battalion post-war stuff hadn't appeared, then a case might have been made that Gruler had at some point accepted the Nazi ideology, but if that had been the case then there was no way the V-Battalion would ever have accepted him into their ranks. The only way it made sense was if someone else had been wearing the armor during the Midnight Sons/Invaders Now appearances, even though it is very doubtful that the writers of those stories had intended this to be the case; more likely they simply hadn't realized they had the character acting so uncharacteristically. Given Gruler wasn't a Nazi it would make sense if he'd lost favor with his masters at some point and been forced to hand over the armor to someone more ideologically in line with the regime. This reasoning was suggested to editorial, who concurred, and a new Iron Cross was born, Oskar Mors. 

Another few official ones.

In Wolverine#26 and 27 Slyde turned up and was killed by Wolverine, resurrected by the Hand and then killed again. This was presumably intended to be the original Slyde, Jerome Beacher, but there were a couple of problems. One was that Jerome turned up alive almost immediately (and promptly got killed again); however, that's annoyingly common in Marvel (not just resurrections, but utterly unexplained resurrections that seem to have come about because a writer simply didn't know the character had been killed), and so doesn't normally require "Doombotting" (to coin a term). However the bigger concern was that in the Wolverine issues Slyde's costume had only a half face mask rather than his normal full face mask, and his skin was pink; it seems no one told the colorist that Slyde was African American. So it seems we had a different guy in the costume. Luckily there was an excellent candidate - Slyde had been revealed to have a white brother in Spider-Man Unlimited#6 (as Slyde wasn't seen out of costume in that story I suspect that again that no one realized Slyde's ethnicity or else his brother would have been African American). It was proposed to editorial that this brother could have been the one in the costume, perhaps wearing it while the original Slyde was in prison; this was approved and so Matt Beacher was confirmed to be the second Slyde.

In New Avengers#35 Constrictor was seen attending the inaugural meeting of the Hood's criminal army, and joining them. The problem was that he was also playing a much more major role in the Initiative at the same time, and seemed to have genuinely reformed (to some degree). So editorial was asked how we should resolve this - was Constrictor infiltrating the Hood's gang for the Initiative? Was he secretly still criminal and moonlighting? Ultimately it was decided that Constrictor's storyline in Avengers: The Initiative was more important to his character than his presence as merely a face in the crowd in Hood's goon squad, so we were asked to suggest other criminals with a similar "tentacley" power set who could have been there instead. Editorial chose Squid, reviving a character who to that point had only had a couple of throwaway appearances and who might never have otherwise appeared again. So if you read New Avengers#35, or indeed any other story that shows Constrictor in the Hood's gang, be aware that's not Constrictor, that's Squid, and please just ignore that they look nothing alike. 

Also tied to the Hood's gang. A couple of times Chemistro appeared in the gang, and was identified as Curtis Carr. Problem is, Curtis had reformed and was unlikely to slip back into crime given that he'd crippled himself while still a villain. So it was ruled that the Chemistro in the Hood's gang was Calvin Carr, Curtis' brother, who had after all taken up the Chemistro identity and was the last known incumbent; he was just telling people he was Curtis as a way of messing with his sibling. 

Talking of brothers, there was also Ox showing up in the Hood's gang (iirc) while simultaneously being seen with the rest of the Enforcers elsewhere (I think they'd been forcibly recruited into the Thunderbolts, but my memory might be off). Regardless, the timings made it hard for him to be in both places. Luckily Ox had an already established twin brother who had taken his place in the Enforcers when the original was (temporarily) dead, and then hadn't been heard of since the original returned to the team. So it was decided that the Ox appearing without the other Enforcers was the twin.