Again here I'm no cable tech by any means, at the same time , the 'error' you think you are seeing , I believe this has nothing to do with your issue. It simply is a reset of your modem, so as it requests network access it has no data stored at that point, so it tosses a ' gee -- I've got nothing' which is spit out to the log.
If i were to take a stab at it , blinded as i may be, I'd say it's a mis config, or time stamp issue between a master and a slave DNS within your ISP. Or considering you've witnessed work, it might be a card in one of the nodes shitting itself.
Hell, even line leakage for this matter. Which pisses off those trying to fly people over your state, and is actually a big issue since lines are aging, and so many line owners have their hands full with new customers they take not the time to run up and down the streets testing.