Break into chunks that overlap by, say, a second, upscale separately and then blend to reduce sudden transitions in the generated details to gradual morphing.

Break into chunks that overlap by, say, a second, upscale separately and then blend to reduce sudden transitions in the generated details to gradual morphing. The details changing every ten seconds or so is actually a good thing; the viewer is reminded that what they are seeing is not real, yet still enjoying a high resolution video full of high frequency content that their eyes crave.