In most cases, this is caused by insufficient power supply condition. Nextion HMIs require a good quality power supply. When the power supply provides too little current, has too low a voltage and/or generates too much ripple, several problems can arise, such as:
- Flashing
- Blurred screen
- Freeze
- Damage to the HMI
A good quality CE-approved power supply is required that can supply enough current and has the correct voltage. If necessary, measure the voltage directly on the Vcc and GND pins of the HMI.