UCC28070 : Phase A does not start / work.

Hi.

I am designing a 2 kW PFC based on the CCM controller UCC28070.

I am quite satisfied because the 1st prototype works.

But one thing I can't explain, is that even if I reached 500W, only one phase of the UCC28070 is working.

Only the phase B is ON. The phase A is inactive. But when phase A becomes active, the output of GDA remains at around 3V, and so, my transistor is always ON...

So, where does it comes from ? I have exactly the same circuitry on phase B and A, and the layout is symetric...

Thanks a lot for your support.