Im not sure how "Clean" that arnold protein is. what i mean is additives, fillers, artificially flavored protein powder. Anything that is typically "Cleaner" will not mix as well,isnt as soluble. I use Vegan pea protein unflavored and it taste bad and does not mix well but its about as clean as it gets besides Naked Whey protein.
ive heard several bad reviews on it but i stick to powders that are not mainstream and not sold in wal mart or costco etc... there's a reason they are sold there and its not a good one