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?
I see you already corrected it yourself - changing https://www.openstreetmap.org/way/243230453 to access=permissive.
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.
I also see there’s a campsite at https://www.openstreetmap.org/node/528571661, and on their website they mention Sat Nav using the wrong access route. If you want that to be reached too consider splitting the road at https://www.openstreetmap.org/node/189763639 instead and setting the access tags on the campsite access road to permissive as well.