Skar Rp2000.1 high rail voltage on low side drain pins??

This one has me befuddled.

Skar RP2000.1 came in with 2 blown n640s on the output side. Pulled all output fets and cleaned up the board. Went to fire up to check for rail voltage and for some strange reason im getting high rail on the low side drains which of course shuts the amp down entirely.

Where would high voltage rail even come close to the low side drains to make a component fail?