You can manually adjust the gimbal tilt (roll axis) in the Fly App during flight, if you have a true horizon. I've had to do that on occasion. Move the gimbal up or down so that one of the grid reference lines falls on the horizon and any tilt...
As tempting as it might be to accept delivery, it is the right thing to do to refuse it, and DJI are not bad guys, so deserve to be treated fairly by us, as they would treat us in warranty situations, which is mostly very good. Best of both...