I have a similar issue with a CECHE flashed with a progskeet. I've used this guide and the ps3 dev wiki one.
Everything goes well until it's time to flash from fsm. I can get the challenge/response from the ps3 entering fsm. No matter what usb stick I try for the flashing, the system powers off after a few seconds. The hard drive has been checked, and several usb sticks have been tried. I'm not sure what to try.
You are welcome. I already contacted him and talked to him about this problem. He told me that this problem always happened in this board version SEM-001 since Samsung U0B NAND chips are very bad and always have a bad blocks.
The best solution for that is to find a spare Samsung U0A NAND chips from old COK-001 or COK-002 board or if you can order it in new condition. So after that just flash your dump into this chips and replace the bad one in the board but that will need a good soldering skills or maybe someone could help you doing this.
I'll try to get this chips and test if my console back to live or not then inform you again about result.