Too many flues!
Just because it's a new build and costs over a million bucks doesn't mean there will be fewer problems. This unit had only two flue-requiring water heaters. I think the rest are being used as fan vents, which will get clogged rather quickly. Other problems included a whistling HVAC return above a gas furnace and next to a gas water heater (combustion components will enter home); the wrong pipe for the sprinkler system (it will melt sooner); water fittings used on gas lines (already rusting); missing and bent deck hangers; many open joints on cladding; poorly hung gutter; paint pealing everywhere on the exterior (painted below 40 degrees?); paint spots and scratches on engineered wood floors, which were recoated to lock in all defects (except under area rugs!); added roof deck over old selvage roofing; upstairs bathroom with no HVAC register; exterior garage door has no home-side controls... may you live to buy another day!