Warranty issue. In need of advice please.

Since they all seem to be dodging responsibility, suggest you try writing a letter cc all of them - dealer, manufacturer, Lippert. Explain that you feel you are getting the run-around and only want it fixed as it should have been in the beginning. You might mention that this has been thoroughly discussed on RVNet and this is the recommendation. Be respectful (even if you don't feel like it), ask them to step up and do what's right and that you feel that since their product caused you to buy new tires that it's only right that they reimburse you. Respectful, but firm. Don't know if it'll work, but couldn't hurt. BTW, keep every copy of anything related to this until it's resolved.