688i periscope depth problem

[Mad Foxes]

Whenever I order pd it tries to surface, after 57 feet I order it again to 67 feet but instead it goes deeper than the ordered depth, I have to keep ordering 67 feet maybe 3-4 times before it follows the right depth. I am playing the mission race of the cripples. I am using the latest lwami and patch is updated. Does anybody have the same problem? Thank you..