4000dvd

i've had rear view camera and had no problem with it.. i m 100% sure nothing wrong with camera.. then i installed p4000dvd with exisiting same wiring from rear view camera.. when i put in reverse, screen doesn't look right..distortion and camera is facing way up high when camera is facing ground.. after few times putting into reverse, rear view looks way it supposed to look.. is this some kind of calibrating issue that i can fix or did i get defective unit??