Apple has acknowledged a defect in the internal screen of the new foldable iPhone Duo smartphone, which went on sale worldwide on October 23 starting at $1,999, Bloomberg reports. Customers have complained of burning and cracking along the central fold of the display after hours or days of use. The company said that the problem affects a small number of devices and advised owners to contact support to replace the devices. In Russia, the cost of the basic version of the smartphone is 299,990 rubles.