VW does not honour warranty

I have a 2015 VW Transporter D/C. The car gave me endless problems. I bought it from a non-franchise dealer second hand, and to tell the complete story it had missed three services. I always took my car for repairs to two dealerships Hatfield VW in Northcliff and VW Knysna. Last year in August the car broke for the umpteenth time and it went back to VW Northcliff. The work they did was to redo the cylinder head, including rockers, lifters and some outside engineering work. The car drove well and went to Knysna where a camshaft broke. VW Knysna refused to honour the warranty on the cylinder head overhaul and blamed the fact that the vehicle was bought from a non-franchise dealer and said that missing services can cause metal fatigue. I have spent over R200 000 in repairs to this vehicle and they now quote me R232 000 to repair the vehicle and are refusing to cover the repairs under the warranty. The only reasons I have my VW's repaired by a dealership is because I (mistakenly) believed that VW would stand by their warranty. If Hatfield VW had not repaired the cylinder head in August last year, I would have quietly sworn under my breath and asked them to fix it at my cost. What makes it worse is that they wrote to me and stated that they have no idea what work was done by VW Northcliff, they have no idea why the camshaft broke but they deny all liability. VWSA quickly followed up with several phone calls to assure me that they will stand by the dealer who does not know why the camshaft broke but won't contribute to the costs to repair the vehicle. Shocking service from VW overall. People should know that the warranty offered by VW franchise dealers is not worth the paper its written on, but they charge accordingly. In a bizarre twist, VW Northcliff offered to repair the vehicle for around R80 000 instead of R232 000. How is this possible? I believe that when I bought the vehicle it was my risk to drive that vehicle with those camshafts, when Hatfield VW Northcliff repaired the cylinder head it was their decision and risk to put those camshafts into that vehicle. That work is covered by their warranty which in my opinion they should stand by.