LNK306PN surge failure

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Hi I am using LNK306PN for one of the Universal motor control application. during our life test its working fine.
during Surge test we are facing some problem. 0.5KV differential there is no problem.
when we put 1KV differential pulse its failing. i don't have a speciality to monitor the output voltage. after test i analysed . my controller is failed which is connected across the 5V supply.

i am using 320V MOV in the supply line. its non isolated power supply.
i have attached the schematic. please help me.

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if your equipment is designed to connect to the mains 24/7 then it cannot draw more than 5mA DC average off the mains - in most EU and related countries ... for earth stake corrosion reasons. Consider a bridge rectifier ...

Also - put the CM choke next to the MOV

Dear Easy Peasy,
Thanks for your update.
we are only using 5min. its in the mixer grinder. so we need to operate 30min max.
i cant use bridge rectifier i need common gnd for the ZCD function.
please clarify why we need CM after MOV. i want to pass the 1KV differential surge test. there is no earth connection in the PCB. only Phase and neutral is there. so 2K common mode it will pass.

Putting the CM choke near the AC input will give you better filtering of DM spikes...