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

[dengpu]

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,

[dengpu]

Here is the design schematic，

[dengpu]

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

[dengpu]

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