First, I suspect repairs involving internal parts made visible would be a lot more common for AI than they are for humans, because while Robot bodies can be made more durable in the short run, the warranty on the parts expires a lot faster without the aforementioned self-repair capabilities of the human chassis. No matter how good your mechanical elbow is, you're going to have to replace it once a decade or so if you use it a lot.
That said, Roko may be less than ten years old in her mechanical body; her simulated growing-up time as a disembodied AI in a software creche on some server didn't involve such physical issues, and they may not have been simulated. So she may be dealing with parts starting to wear out for the first time.
Speculation that maybe she is a copy of a human mind currently running as an AI in a robot chassis would be another possible reason for her to be unfamiliar with this kind of repair - but that brings up a host of additional issues, such as whether and where QC medical/AI science is that advanced and how she feels about the 'life left behind' of her biological predecessor, and how the people from that life (parents, friends, lovers, children ... great-great-grandchildren?) feel (if they even know) about her. Does she visit the gravesite of her biological 'parent' every so often when she needs to think about the 'meaning of life', or just to pay respects and leave flowers?
Whatever the shape of Roko's issues in detail though, I can see Bubbles taking advantage of Roko's momentary "Downtime" to explain to Faye that they're going to be giving her a deep discount and an apology, and in the future please show more respect for the sensibilities and sensitivities of our customers, both because we don't really want to be known as assholes and because showing the same respect for people's issues about their mechanical bodies that you'd show for their issues about their biological bodies is the right thing to do.