The way the RD works is the cable pulls it in toward low gears against a spring that returns it to the right when cable tension is released. It's possible it's a simple centering adjustment, though that should affect all gears. Or the device in your levers that engages the clicks is weak and the spring tension is enough to pull it out of gear.

Given that it's a new bike, you should return it to the point of purchase and have them resolve the various issues, plus better explain to you basic utility, and user adjustments.