I have been dealing with this problem for few months, I was using bootcamp on my iMac late 2013, and after a while its driver corrupted using too much disk space and slowing down. So I deleted it and created a new bootcamp partition but my problems didn't end there. Every time I shut down my computer its windows files would corrupt again making me redownload windows. And few days ago this corruption affected my main iMac drive too. I can repair the disk through disk utility because its giving me exit code 8, my internet recovery mode is giving me code -2002f and its startup is extremely slow ( only the part where you enter your password and log in) everything else is fine. Startup problem is the same problem i had with the bootcamp. I was getting black screens during startups. I wasn't able to delete my bootcamp partition until today because the disk utility didn't let me to do it. I deleted it through terminal and now I am dealing with my main drive corruption. I plan to sell this iMac very soon due to educational fees and I want to fix this before I sell it. I am currently trying to log into single user mode but its keep failing to mount disk0s2 and there is a small white circle with a cross on the screen. How can I fix this? Would formatting my iMac solve all my driver problems?
The 2013 iMac was offered with 1TB hard drive, Fusion drive, or SSD. The first two of these use mechanical spinning platter hard drives, which are expected to have a limited life before failing.
After six years, it's likely that the drive is failing, and so Erasing or repartitioning it won't help. Replacing the drive is possible, but "moderately difficult".