it isn't the shub over heating which is causing the problem, it is the heat outside which is affecting the coax, resistance and attenuation etc. If the shub is coming up with errors in the log it will more likely be due to the fact that it can't connect to the cmts due to the out of whack power levels rather than it thinks it is too hot. It will return to normal as it cools down over the next couple of days. -6 is the lowest you really want to go on the downstream.
Edit: just had a look at mine and they are very similar to yours but I wouldn't have noticed it if I hadn't have checked. I have been merrily downloading stuff all day.