PS4 Safe Mode

My sons PS4 is in safe mode I plugged the remote in and tried the restart. Came back to safe mode. Then told me to download the reinstallation 6.20 or higher on a usb drive. I’ve done that it will do the download then once downloaded I goes to restart but once restarts goes back into safe mode. So I erased everything and started fresh. Less than a week later it went back into safe mode again. I tried this time to download reinstallation from internet did that and when restart back to safe mode. I don’t know why or how to get off safe mode other than erasing everything.