Wow!!! i have a the same story! Just got our 20201 Jeep last month. The back up lines started disappearing a reappearing the first week. I am waiting for them to come up with a fix as well! this is ridiculous!
Please feel free to send our team a private message if you'd like additional support while working with your dealer to get your concerns addressed. I'd be happy to look into your specific situation and see what we can do to assist further.
I also have a brand new JLU Sahara 2021 - issues with my backup camera guidelines coming and going. What is the fix? I don't want to spend my time at a dealership with my brand new vehicle.