I believe this to be a type of fluke as well. It looks greyish and kind of like a broken mushroom which means it must have been a bigger one and quite old. You need to continue the prazi alb combo until after you don't see them anymore, might take months depending on your infestation. Also afterwards i would suggest to do monthly doses to see if you missed any and for prevention. After you clear most of your flukes out, it is usually easier to clear roundworms too.