Inquiry About Issues in 60W (12V/5A) Converter Design Using InnoSwitch4-QR

I am currently developing a 60W (12V/5A) converter using the InnoSwitch4-QR. I have designed and built the circuit by referring to the application design, and I am conducting experiments, but I am experiencing some issues.

Based on the current test results, I have confirmed that the desired output appears normally when varying the load conditions and input voltage. However, for the following two reasons, I suspect that the secondary-side controller is not operating:

1. When increasing the load, excessive heat is generated at the SR switch, and when I checked the SR Vgs, there was no PWM waveform, so it appears that the MOSFET is operating only as a body diode.
2. I cannot observe Valley Switching at the main switch. (As far as I know, the principle of detecting Valley Switching is through the waveform of the secondary-side Forward pin.)

Therefore, I suspected that the secondary-side controller is not being supplied with sufficient voltage, so I measured the BPS voltage and found it to be around 3.5V, which is lower than 4V. (There is momentary noise only at the switching moment.)
To increase the voltage, I increased the BPS bypass capacitor value (from 2.2uF to 4.4uF) and conducted the experiment again, and I was able to confirm a BPS voltage of about 4.5V.
However, the same problem as before was not resolved, so I would like to ask for your help.

The attached photos show the results of the experiment after increasing the BPS bypass capacitor value. (Yellow waveform: BPS Bypass / Purple waveform: SR Vgs capacitor voltage)