[ADTech]

The C4 is TOO directional to be expected to reliably pick up a UHF-15 station that far off bore-site. A C2v, with its 70* horizontal BW and a simple VHF dipole, would have been my recommendation for a better fit.

Try cheating the aim more northward to see if you can find a spot that makes everything happy. While I'd like to see it happen, but I'm not optimistic. The "classic" solution is to use a separate UHF antenna aimed directly at the ION station combined with combo aimed southeast via a UHF 15 Jointenna. Unfortunately, those products are becoming increasingly hard to get a hold of. The only seller I know of is Warren Electronics.

If you want to experiment, pick up a generic matching transformer, and connect to only 1/2 of the C4 (remove the combiner (carefully!!! first) and split the difference between the main cluster of UHF stations and that ION station. You may find this will correct your reception of the ION station and the rest of the UHF stations but at the expense of your VHF station (no free lunch here). That can be addressed separately.