I recall, on a visit to the Ilford/Harman factory, the manager at the roll film line mentioning that special printing ink has to be used on the backing-paper to avoid print-through onto the emulsion. (The printing is, of course, in direct contact with the emulsion surface for the whole time the film is rolled on the spool.) I've seen this print-through myself on a very old B&W film.

If there is no obvious light-leak issue, I'd try the camera with a fresh film.