[GeoffR]

Does the fault exist in the original Adobe DRM epub version (downloaded from the website) or is it only in the kepub version sent directly to the Kobo device?

If the fault is in the original epub then my experience is that it is better (i.e. it gets fixed faster) if I complain direct to the publisher. From what I hear Gateway books start out with a lot of OCR errors, but they are very good at fixing them when reported.

If the fault is not present in the original epub then it is purely a Kobo problem and there is no point bothering the publisher about it.