So, I posted with a bunch of links to old posts, but this is what I was thinking:  I am assuming that the gizzard has a valve at either 'end' (coming into and exiting the gizzard) to regulate inflow & outflow of food.  (? I don't really know if they have valves in their intestinal track like humans, but would assume ???? that at least in the gizzard they might??)
Butters pooped a whole lot of fibrous material.  The initial poo was so large/bulky that Butters couldn't get it all the way out on her own - 
@ChicoryBlue had to help by gently but firmly pulling it out for her...and Butters went on to have another 1 or 2 poos made up mostly of long fibrous material - though none as bulky that she couldn't pass it herself.  I was thinking that maybe, if she had that much stuff in there, and it was 'stuck' in the gizzard (remember, her crop was backed up with sand-like grit - so something must have been blocking her track below the crop), that maybe the 'exit valve' to teh gizzard got stretched/damaged, and that is why small solids are showing in her poo???  That the gizzard isn't 'sealing' properly, and stuff is exiting prior to being fully ground?
Only a pondering on my part, as I don't know the anatomy as well as I should.  I have seen a gizzard, but never inspected it prior to opening it/cutting off the rest of the tract to examine to see if valves are present.
I was hoping someone with a better understanding of the chicken digestive track and it's functioning would know if it had valves, and if they could have been stretched or damaged (if present) if they could heal and/or the gizzard adapt over time.....i.e. eventually she wouldn't poo unground things.
Ramblings of a curious but uninformed mind about potential causes.  I do suspect that whatever is wrong with her, it has something to do with the gizzard given that undigested pieces of 'hard to digest' items are showing in her poo (hulled sunflower seeds, kernels of corn, etc.)