I’ve got whatever the latest Beta is, and was running the previous Beta since this (well, yesterday, now) morning. I haven’t seen any issues with the grid guide since then, save once: When I briefly went into a channel, then back out again, right about on the hour, the guide was broken. The selector would be on a certain program and channel. When I tried to go “up,” the selector would just plain disappear. Go back “down” and it’d reappear where it had been.
There was a narrow margin of increased black space to the left of many of the guide entries.
I went to grab my phone to video it. But by the time I got back, a minute later, the guide had refreshed itself and the problem was gone again.
I suspect it was into that black space the selector was going. My guess is some of the guide’s program logic thinks there are still entries there, but the entries are no longer rendered on-screen, so the selector simply disappears.