What is connected to the output, P0 and P1?
what is the capacitance of C400V Power Cap?
how much current is in that 680 nH inductor feeding the bridge rectifier?
I built a switch mode power supply once that was current fed instead of voltage fed
when the FETs switched, they kept blowing up
the drive was designed for a voltage fed system, so all of the FETs were off briefly
when switching legs (from Q0/Q3 to Q1/Q2, and back, etc)
turning off all of the FETs removed the path for the current and it blew up
when we changed the drive so that all of the FETs were ON when switching legs,
it worked fine.
i don't think that's your problem, because of the capacitor on output of the bridge
but if its a high current feed, and the capacitor is small, then the voltage can rise enough to blow up the FETs