When he was first introduced in the manga, he's actually quite as smart as Atom is- at the very least, he can do math quite as well, evidently. But he couldn't properly disassemble and/or reassemble that alarm clock; because of this he was described as "not very good with his hands", but I actually don't think that that has anything to do with that problem. It seems to be implied that a robot has an innate understanding of machines and how they work and fit together as individual parts, which makes me think that they can do much the same for their own bodies (quite unlike human beings and their own squishy bodies). Cobalt, for some reason, lacks this kind of understanding, which, considering the implications, makes his seemingly melodramatic meltdown after the fact make much more sense. This would be an almost crippling disability, wouldn't it? I don't even know what to call this, or if there even is any sort of human parallels.
When first introduced, and indeed, seemingly after being reintroduced, he didn't seem terribly clumsy at all, unlike in the show. Even then, that could be chalked up to his low fuel, or perhaps just bad luck. He was a little goofy in both (post reintroduction in the manga), but there's no way of knowing if his AI was supposed to be less perfect or not (although considering that not much was evidently changed between the dub and the original, as far as plot is concerned, this being any different is unlikely) in the original, considering that, as far as I know, it may not even exist anymore.
I have no idea where I was going with this, or if I ever had any idea. :T I just wish he was a little better developed (he could have been in the show, but since most of his appearances were never translated, and are unlikely to ever be unless one of us commissions a fansub group idk), and that I got to see more of him around. He didn't have a lot of time to experience much development at first, before he was (quite violently) killed off after an unfairly short time. After that, he was written much as he seemed to be in the show, to the best of my knowledge. And just as then, he was either a plot device or comic relief- or even just there, in the background, with no speaking role (side-eyes Medusa's Mansion or whatever it's called).