LM5021: two-transistor forward Topology using problems

Dear Team,

     My customer is design one AC-DC  power board based on  LM5021MM-2/NOPB . The topology  is  two-transistor forward .

    Vin= AC 220V，Vout= DC 27.3V   , Iout(max)= 20A，Transformer ratio is 2.5:1， second side filter inductor is 180uH（about 54uH@20A),

    Ｃout=470uF×4（ESR is 54mohms each Electrolytic capacitor）。

Problems :

    Below is the wave of   Vds, when Iout = 2A.  It looks worked  not very well.

The compensation part of the schematic is as belows:

I can't  get better results through tuning the compensation controll circuit.  So , 

Do you have any reference design or technical material about the LM5021MM-2  working in a two-transistor forward converter？

Or could you help tell me how to solve this problem?

Thank you very much !