I have two Grand Designs. A '16 29rs and a '17 220 rk. I have had lots of little things wrong with both of them. The only major thing was the Lippert brakes that had grease on them. GD made me call Lippert instead of them handling it. I did get new brakes but installed them myself. As the other poster mentioned above GD used to go above and beyond on service and extend the warranty for years past it's expiration date. I had a couple of plumbing parts go bad and they said I had to buy them.
I paid a premium for both of these RV's but will not buy GD again unless I can get a price comparable to a FR. I had three FR (Nitro, Surveyor and Columbus) prior to these two and had no more or less issues with them.
Looks like if you want a chance of getting anything from GD for free you have to get on one of the Facebook pages and cry.... They may help you that way. They are also bad about deleting posts that don't show GD in a good light.