Cannot update Firmware, stops at 67%

I have tried to update the Firmware multiple times because my PS3 just randomly shuts off every time I use it. I have used the Safe Mode almost every time, but to no avail. It always stops at about 67%. I have heard this is a Blu-Ray drive issue, but I have a second PS3 (same model) and I tried swapping them. I kept the daughterboard to the same PS3 that it was supposed to be with, but it stopped at the exact same spot. I don't know what to do.