Go back to the basics, the synthetic forend is much harder to "tune" than the wood forend. As it wears at the frame pivot point, it's going to change how it fits and thus change how the rifle shoots. If the survivor forend was tight, you have part of your answer. Maybe it's time for a forend change?? Epoxy?? Where?? If it locks up tight and there's no gap at the breech, epoxy isn't the answer unless you use it on the forend to tighten it up, but a new forend would be more practical, I think....maybe a wood forend and paint it black, the spacer on it allows some tuning for fit.
Mac's right on making sure everything is tight, to include the stock bolt, someone posted about a ruined hunting trip cuz the stock bolt was loose and they had no tools to tighten it. I'd loctite it, too!!
Tim