[Turtle91]

I don’t think it’s giving an error on the split itself…. It looks like it’s just warning you that your links aren’t set up just right and they will/might break when you split the pages (because your target would be on a different page). There should be an option to continue anyway (if you don’t care about the links) then you can fix them afterwards. If you only have a few links that is not that big of a problem.

Have you already merged the document into one large file? You can also run a report in Sigil and one of the options on the left side shows the status of all your links.

EDIT: What Kevin said…