After weeks of lockdown, a slew of staff at a Chinese tech factory struggled with officials and ran through isolation barriers, a staggering collapse of the Communist Party’s efforts to save COVID-19 infections. Since the beginning of April, the Shanghai plant, which belongs to Quanta Computer Inc. Taiwan and produces devices for Apple Inc. and others, works under strict limitations. They broke through barriers and collided with guards in white security gear who tried to keep them inside, according to a video posted on Twitter and YouTube. Quanta workers showed the altercation took place Thursday night, but the company did...