Could just be a timing issue, a 1 frame delay (child segments are set before their parents are updated, each frame).
Either way, you should re-think and re-code your approach IMO. Use one action and a single loop for the creature and position subsequent segments iteratively/ via skill linking (loop over main segments, like 10 starting tentacles, then move forward via skills, pointers (faster) or handles (suitable for game_save)). No additional while loops in the segments.