@Ulco, I tried lowering the samples to .25/5, AA to 6; it does save a little time, but shadow jitter on mtns are more noticeable, and "shadow popping" is still there.
@Hannes, thanks, you might be right, I don't believe it's a shadow pop (in foreground) anymore, thanks! it appears to be something weird with the grass clumps, and other than changing the render quality, which I've tried them all, I don't see any other parameters to play with, unless there's something in the density or terrain shader inputs of the grass clumps that I have going in to it.
@Oshyan, I'll send in the tgd, but what do you mean by "depth sorting"? Is there something I can try to test it out? I did a test with AA at 12, no change.
Thanks.