The early caliber 324 movements are non hacking. Meaning the balance wheel of the watch is still moving as you adjust the time, meaning the train wheels and escapement are still in motion. Adjusting the time clockwise in this case as Legend mentioned earlier is the natural movement for the train wheel and causes no problem. But when you go counter clockwise. You're essentially causing the movement to jam up and stop moving in it's natural direction forcefully, (think throwing your car into reverse before you've come to a stop) giving you that jittering seconds hand. Once or twice is not going to kill your watch, but you're really putting unnecessary strain on the movement by doing so.
Oh man, i should have read this before!
I always thought its not a good idea setting time counterclockwise, but one time i did it and now my new aquanaut is broke (looks like hour hand is stuck at 11 o'clock, at least i cant set time past it).
And of course its the only movement you cant get spare parts...icard:
But thank you, at least now i know it was my fault and i will never do this again!