Why do organs jump to a higher pitch on G?

This is supposed to be the melody of a pipe organ piece. However, when I play it, the G jumps an octave higher. I changed to regular organ, and it does the same thing. I actually play organ. I can usually get two or three octaves out of one manual keyboard. Is this a bug? Or is this really the way organs are supposed to sound?

This is an audio tutorial. I may have to change instruments to get the octaves in the right place.

Thanks for everything!