IW3627 iTHD(%) issue at 32 W

Hi,

We are encountering an iTHD issue in our product. Specifically, at 32W power and 230 Vac, Over time, at certain instances, it reaches 22-26% and it is repeating continuously in the long run. We have verified the resistance and capacitances values for FB (Pin 2) and CS (Pin 4), and they are within the recommended range. Could you please provide clarification on the potential causes of this issue? For your reference, I have attached a screenshot of the input voltage vs. input current waveform.