I have the exact same 2017 camper, just had mine at dealer for 2.5 weeks. I own air conditioning company and told them what was wrong, factory was no help finally have them two options. Unit is short on air flow, roof is to restrictive, they could either add a return directly under units with dump zone dampers for quick cooling or remove entire roof and rebuild. Factory never did get back to dealer but they put in returns and that done the trick. I will add pictures later for you.
2017 Columbus 377MB pulled by 2016 GMC Denali 3/4 ton