It would appear that part of Dalby Forest Drive (south of the visitor centre) is incorrectly marked as private. This leads OSM based sat navs to route around the forest and access the visitor centre from the top. Some roads around there are private though.
Would anyone from the community with local knowledge confirm this and assist with making the relevant corrections?
If access is allowed until the visitor centre but not north of it, it may be better to split this road into two parts. You can do that at node https://www.openstreetmap.org/node/310532383, then you can tag the road to the north as access=private but the car park can still be reached.