I suspect you're doing better than average... Combining two dissimilar UHF antennas is usually a 'roll of the dice' and the 'dice' are loaded (not in your favor). The problem with combining two antennas is that they will both receive different versions of the same signals. When mixed together, the two versions can add to make a stronger signal but just as easily (and even more likely) the signals can work against one another. The TV tuner is often left to deal with the RF equivalent of being stuck in an echo chamber, even if there is lots of signal power, it may be garbled and hard to understand.
Consider - The 4228 was receiving signal from the two problem stations when it was the lone antenna in your system. You've done nothing to stop the 4228 from continuing to receive a poor quality version of the two signals. Though the strength was above 70%, it was unreliable which is a symptom of multi-path, as is the UPS truck symptom. So now you may or may not be receiving a high quality signal from the two problem stations via the 8800. If you are or aren't, mixing the low quality signal from the 4228 insures the net signal quality is going to be less than ideal.
KAIT is operating on real CH-8, a High VHF frequency. An Antennacraft Y5713 would be a better choice than any UHF-only antenna (which the 4228 & 8800 are). Still, the signal from KTEJ is broadcast on real CH-20, so you need a UHF antenna to be able to receive it.
Even the most directional TV receiving antennas have forward-beam-width of at least 15 degrees. There should be no need to fine tune antenna aim in increments less than 5 degrees. Long before I tried 'fixing' this reception reliability problem with a rotator, I would test reception conditions outdoors in the clear.
You may need more than one antenna, but I would try a single medium gain all-channel antenna mounted outside, clear of the electrical noise generated in your home, and clear of the reflections and signal attenuation of the attic.
If we were neighbors, you'd likely see a Winegard HD7010 or similar antenna above my roof.