Please stop saying you're "getting" all the channels listed, then turn around to say they "go in and out on a regular basis." Here's the proper way to say this: "I CAN'T GET ANY UHF STATIONS!!" That's the correct, accurate thing to say if you want to get serious help from busy people. Nobody is surprised by this. After all, you have only a VHF antenna installed indoors. Let's say you get a UHF station 85% of the time. That does NOT count.
I don't know how you can even tell that when 66% of the metal up there is doing nothing but causing multipath. This could be a huge factor, or it could be nothing. IMHO, you have to fix this before you know anything. You might not even need a second UHF antenna.
I hope all that clarifies my status. Please excuse my lack of knowledge in the field of technology, but I'm always willing to learn. Don't I deserve some kudos for trying to be a DIY'r "Cutting the Cord"?