If your chapter videos are in separate timelines, then the skip forward/backward navigation is completely dependent on what the individual DVD player will allow.
You may have better luck with the navigation issue if you add your chapter timelines to a standard playlist. En *may* program the commands differently enough in the playlist so that navigation is easier for the DVD player. I haven’t tested that particular feature for your kind of navigation in a very long time. 🙂
-Jeff
The Focal Easy Guide to Adobe Encore DVD 2.0