the stamp on the left its centre is shifted upward during printing so this make the dotted portion upper the Dam photo smaller also this shift make the part under the word"OWEN FALLS DAM" looks different in the left one it contain small dashed lines in blue color under the black lines while in the right stamp it just blue lines not dashed under black lines also the centre is shifted to the left about 0.5 mm thats make the white area in between the left black and blue lines disappear.
the another stamp is also the centre is shifted to the right and upward so the crown is more nearer to the frame and upward to be between the upper lines
Slight shifts in the registration of colors is extremely common and within acceptable production quality. Look at almost any multicolor printing - a magazine, poster, newspaper, etc. The small shifts you show would not be considered significant enough to be errors, freaks, or oddities.
@John Becker you are right but some stamps got shifts more than others I think this issue got more shift than other issues also the first stamp the shift change the design slightly in left down corner I just see only about 100 pcs from this stamp the shift is less than that I didnt got thousands to make a study, I only see one piece with more major shift than that alter the design in a collection of a friend.