Multipage only works in Blu-ray, so just wanted to be sure I knew. I don't think that could have been the issue anyway...
There have been issues with buttons created using index. See this thread for examples.
Re: Encore Chapter Indexing Error
In any event, if it is just the previous/next, just correct them manually. If it is more than that, try posting a screenshot of your Encore flowchart here.
I can't find a note, but I think the easiest way to handle the "can't execute" problem is to remove the end action on the final chapter.