I have hundreds of feet of spaflex in my plumbing and have for years
no issues, but I dont get chunks coming off of it either
At first I thought it was just glue you were seeing but then I read closer and its been running a while you say, so unless you just slopped the glue on inside every joint you should be way past finding pieces fo it. I imagine what you are seeing is inert and nto to blame for your woes.........BUT, pieces coming off isnt normal and the stuff I use is the same as what home depot sells but their prices are insane for the stuff.