Some of the code run from your computer is in the cache on your computer (and likewise on your readers computers). And remember that the content of the cookies on your computer may affect how the code is used.
If a change that Blogger makes includes both a change to the Blogger database, and to the Blogger code run from your computer, the code cached on your computer will be out of date, and may cause problems.
Maybe the Blogger code on your computer (cached yesterday) is processing your Blogger blog, which includes a new option (added today). The code sees the new option, and not knowing what else to do, ends its progress with a bX- code. That's your computer (running the Blogger code) saying
Hey! What should I do now?
So when you have a problem, like maybe seeing a new bX- code, and Blogger has just made a database change, sometimes they will suggest that you clear both cache and cookies, and restart the browser. That's not Blogger making you jump through hoops, that's them asking you to help them to help you. And there's no "secret key sequence" that let's you "bypass the error code screen", as some trolls try to tell you.