ID:273487
 
From the DM Reference:


SYNC_STEPS is intended for objects that move in unison as part of a larger "conglomerate" object. You should set the movement animation to SYNC_STEPS on all but a single "head" object, which will serve as the leader when choosing pixel step sizes. If you do not use SYNC_STEPS, there are cases where the pixel offsets of objects may get out of sync during motion, causing the object to visually break up.


How would I make a "conglomerate" object?
By having multiple objects be treated as if they were a single object.