@f1ee7a25  Don't forget, be booted from the external to install. 

 @f1ee7a25 I'm wondering whether it might be bad piece of RAM, or possibly a mainboard issue.You could try installing Ubuntu on it, see whether their hardware diags report anything. Linux tends to be more transparent than macOS about what state the hardware is in. 

 @f1ee7a25 Yeah, with the later versions of macOS, you need to install a full environment to an external hard drive and then boot the target machine from that, then install to the internal drive from an downloaded installer on the external. Lots of problems trying to just do it from a pen drive. 

 @f1ee7a25 Okay, so it’s in the setup stage, hasn’t properly started replacing files yet, and it isn’t throwing an error code. Tell you what, boot recovery mode and rePARTITION and reformat the drive, then try an install again. I feel like there’s something locked or corrupted or something that’s making the installer fail when it begins trying to manipulate files on the drive. 

 @f1ee7a25 What’s the error code the install is throwing again? 

 @f1ee7a25 What does Disk Utility say? Maybe boot recovery mode again and do a check. 

 @f1ee7a25  Try starting up with Option-Cmd-R, and see what Internet Recovery gives you. It might be failing because the old installer on your recovery partition isn't signed any longer. 

 @f1ee7a25 You reinstalling from the installer on the recovery partition, from an external drive, or from internet recovery?