UCC3895: [UCC3895]Questiones of UCC3895

good day,we used peak current mode control to impelement psfb by UCC3895,and find something abnormal ,the test condition is Vin:400V,output l2V/70A,what's function of UCC3895 caused this?  Dead time:100ns,SR PWM duty very close to 100% ,if i increase dead time more then 100ns,this issue has gone, so i don' t think it's layout/noise issue ,, i'd like to know what kind of mechanism in UCC3895 which could result in consequence like this?Thanks.

CH1:CT signal after rectify(Yellow)

CH2:primary side mos gate signal(Pink)

CH3:sr gate signal(Blue)