The development of the Czochralski （Cz） method for growing monocrystalline silicon has facilitated the production of larger crystals. Currently， in the repetitive Cz process， the weight of final crystal in a single furnace typically reaches 600~800 kg， exceeding the engineering load limit of pulling cable in established technologies. This paper reports stability issues arising from increasing the diameter of pulling cable during equipment upgrades， along with corresponding solutions. The study reveals that the increased rigidity of the thicker cable causes seed crystal tilting， which leads to ridge line deviation under low-load conditions and elevates the risk of neck fracture under high-load conditions. Through controlled variable experiments， this work confirms that the stability issues in crystal growth after cable thickening primarily stem from seed crystal tilting. Furthermore， numerical simulation methods were employed to analyze the stress distribution mechanisms induced by seed tilting. Ultimately， stability in crystal growth was successfully restored by adding counterweights.