When MP8759's output voltage is configured to be 12V, the output voltage is abnormal

In our power supply design, we use MP8759. The input voltage is 20-25V (24V nom), the output voltage is 12V,
This is the ouput voltage’s waveform from oscilloscope,

Here is the design schematic,

Here is the waveform at SW point. From the waveform, the duty is always changing.

I find the problem. The max output voltage of MP8759GD is 6.5V.