Yikes! $52.00 for that? I need to raise my prices. For $13.00 more you can get a feeder with a door, one that has a feed lip to help stop most birds from billing feed (they have one, turned outside instead of inside, go figure), and a spring loaded door and counterweight that will stop wild birds and rats from stealing the feed.
As for salvaging what you have, they have some sort of wire grid inside. Does the feed flow outside that grid? A grid is supposed to prevent billing, sweeping food around using the beak. A chunk of chicken wire will help as long as it is laying on top of the feed, might have to remove their grid and secure the chicken wire somehow. Or get a roofing tin water flashing shingle at the big box store that is long enough to trim down to reach dise to side inside the feeder. Cut it about three inches wide and bend a lip on one long edge and insert it between the front of the feed tray and the sides of the feeder right above the pop rivet. That is a lip extender, makes the feeder deeper, harder to fling feed.
That said, mixing feeds leads to birds sorting feed looking for goodies. Put one kind of feed in a feeder and use multiple feeders. Or buy a good feeder for a few dollars more. I know, shipping, those are
Amazon Prime, the shipping is buried in the cost of the feeder.