It’s an artefact of the way the footpath is tagged in OpenStreetMap (which cycle.travel uses as its base data). Generally cycle.travel is happy to be dragged onto a footpath as long as it’s not actually tagged as ‘no bicycles’.

The area you’ve found is a bit strange in OSM, as they’re tagged as ‘tracks with the legal status of footpath’ (more or less!), which isn’t a combination that cycle.travel knows how to parse. I’ll see if I can tweak it to allow pushing along this combination.

Thanks Richard, I'll check back in a week or so and see if it's working.

Hi Richard

Resurrecting an old thread here, but I'm finding more and more examples of the waypoint refusing to snap to tracks. Some of these tracks are even bridleways, though it appears openstreetmap thinks they're footpaths. 

Honestly it's makes planning mixed routes with this site very frustrating.