DC2596A : LT8708 Development Board ZVS of MOSFETs M1 and M3

Hello, 

     I am working with LT8708 development board DC2596A, for Battery charging application. I was able to get CC-CV characteristics required for Battery Charging on Electronic Load. While observing the Vgs and Vds waveforms of the all the four MOSFETS, M2 and M4 were switching as per ZVS but M1 and M3 didnt have ZVS. 

Input: 60VDC

Output Loading condition : 1. 42V 7A (Buck Mode in Constant Charging)  2. 63V  6A (Buck Boost Mode, when battery charging enters CV Region)

I have  changed the Gate resistor for all 4 MOSFETs =4.7ohms

Request you to help out, why M1 and M3 are not having ZVS? 

Please find the attached Image: