Here are a few suggestions...
Bypass the corporate service department at Newmar and contact one of their VPs. If they aren't interested in helping let them know the other options you plan to use to get the problems resolved. Include calling executives at Winnebago since they now own Newmar.
Another option is to contact "On your side" departments in television or print media companies.
If you are not getting satisfaction and decide to go the legal route, then check out this post from RVTravel.com
https://www.rvtravel.com/fixit/
Next, do a Google search for "RV Attorney" or "RV Lemon Law". Here is an example of one law firm:
https://rvlemonlaw.com/. Note that I am not affiliated with them in any way.
Good luck in getting your issue(s) resolved!