Error Code SU-42118-6 (Stuck in Safe Mode)

Hello,

I recently purchased a ps4 fat with (I believe) firmware 6.50. I bought it under the assumption there would be an issue (there was). It turns on fine, then shuts off, turns back on into safe mode and asks me to use a USB with a firmware update 6.50 or higher. Once I do that, it errors out and gives me the error code (SU-42118-6) and tells me to power off the ps4. I boot it up into safe-mode and all the options grey out besides initialize and it all leads back to the USB into the error message. I have quadruple checked the USB is set up correctly and I have confirmed the correct firmware is installed (I tried 6.72 & 9.00). The warranty stickers are all missing so there's definitely been someone in the device prior to me. I tried a new HDD and different data cables (it was missing when I opened it originally) I'm not sure how to decide to proceed. I'm set on fixing the device so i'm curious if I should dive in on checking if the daughter board is working properly or if replacing the drive itself would possibly fix this issue.

I reached out to the seller and they said they have no idea what happened since its been so much time. I got it for cheap so, I'm not concerned about a refund or anything of the sort.

Any advice/info on this topic would really help my headache.

Thanks everyone!