Docsis Engineering has become QUITE careful prior to pushing out an update, Years ago, they pushed an update to the Netgear 6300's in the hampton roads area, (I know, I had one), and it bricked it. I was provided a brand new modem at Cox's expense because of that. Trust me, they have become far more rigorous in testing.
All updates, whether you have a Cox modem or a third party modem, the firmware goes through serious testing at Docsis Engineering, prior to getting pushed out, There is nothing like bricking 3000 Modems in one night, and having to be responsible for replacing them...