This company sells defective products, knows it and doesn't care.
When I ask about my two clocks being several seconds late every day, here's their answer (copied and pasted from an e-mail) "Due to internal space and power consumption limitations, we cannot integrate a hardware real-time clock (RTC) or wireless time synchronization module. The time deviation within 24 hours is approximately within 7 seconds. In order to solve the time display delay problem and minimize the error, we recommend manual calibration, which needs to be calibrated every 24 hours. Please note that despite limitations, we appreciate your understanding and value the opportunity to provide solutions." So if you buy a clock from this company, be prepared to adjust it every day, it's normal...