Do you have a video showcasing this glitch? If so, post it over at Sonic Retro if you are a Trial Member. DarioFF, S0lV0, and Twilightzoney are fellow Tech Members who know the inner workings of the game, and would most likely be able to explain why this happens. I've never encountered any glitches while playing Generations, but it's been a while since I played it. Was this on the steam release or console?