I don't know about full fledged flashbacks, but I know you can kind of "force" them after awhile. Like just staring at stuff until it turns wavy, or times when you look at something and for a second it's the only thing you can see. I know it's not just me, I remember mentioning this before and I think Leary was one person who says he gets this too. Knowing me and him, it could possibly be acid that's causing those little moments, but it could also be shrooms... or dex... or pcp....?