Hi There!
Wow this is a brand new unit, any repairs should be covered under warranty but I can give you some ideas. There could of been air in the system from the tank not being purged correctly. I would suggest to have your LP system pressure checked, this is essential for proper operation. Your motor home requires 11" of water column for all your appliances to work correctly, the stove has it's own regulator and if it were to malfunction it could cause your issues. I would contact Newmar Technical support and let them know what is occurring.
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RV Mechanic
10 Years RV experience... Cummins North West, Country Coach, Monaco Coach, Vendor certs.