While many of the Sonic games had some degree of flawed writing consistency even from the Genesis era (Hello, faster-than-Sonic Eggman!), from what I've seen the big continuity snarl (Other than Sonic 06, which un-did it's own story anyway) was "Sonic Forces", a game where characters from previous "modern" games (Or, when you consider episode Shadow, Infinite in the main game himself) acted in ways they clearly would not have had in previous entries in order to justify what the next plot development was. Most of the other game entries, even if they were lore-breaking like Lost World, had the wrong tone/atmosphere like Unleashed and Colors, or ignored previously-established character traits like Heroes (loner Knuckles who doesn't trust Sonic? Yeah, forget that. Also the entire Chaotix character profiles retcon.), weren't nearly as glaring about it (Let's face it, you probably didn't really care that Knuckles and Sonic were teaming up right off the bat...), or attempted to justify it in the gameplay mechanics (... or that Lost World suddenly takes place in a setting where everything is planetoids)- things which were not adequately done to any degree in Sonic Forces, a game that tried to pander to fanservice when it didn't actually understand what people liked about the very fanservicey material they were trying to make. It'd probably be too simplistic a solution to say "Just ignore Forces", although I suppose Sega can somehow manage to screw things up while still technically fulfilling that suggestion. I think ultimately the big problem is that clearly there's no real "Sonic bible" anymore; Iizuka clearly just makes up the lore as he goes along and changes it when it doesn't suit what he wants to do next, to the point where he's lost concern for any sense of consistency. He has very few apparent hard rules outside of "Classic Sonic doesn't speak", "Classic Sonic music can't actually sound authentically retro", "There must be guitar riffs in music associated with Modern Sonic" and "Even when we promise Sonic is the only playable character, we have to keep adding new characters to a Sonic game's character roster." For Sonic writing to maintain any sort of consistency, a bible like that, with at least SOME hard rules, must be maintained. It doesn't have to be as specific or as weird as the western Sonic bible we've previously come across, but it at least needs to say "This is what Tails' personality and skills are, and how he'd act in various situations", "Here's some stuff Shadow would NEVER do no matter how edgy you want him to be", and "Here are all the possible motivations for Knuckles to get involved in a story, as well as who's side he'd be on in association with those", and probably also "Here's some elements that could be in a comedic episode or a serious episode, but not both."