This is normal behavior. The reason we have it setup like this is so that webmasters can see the hashes are being found. Because we have quite a lot of volume on the network it’s not possible to submit every hash so hashes that don’t match the required difficulty aren’t submitted. The difficulty is a number we can change from here to match the network volume and balance load. Bare in mind that the publisher system rewards are based more on unique visitors than hashes found.