The drives you get back when you RMA a drive are almost never new, they are other people's returns that have passed diagnostics. That means you could be inheriting someone else's hard to troubleshoot problem drive. Whenever possible, return for refund and purchase new, even if you have to pay a penalty.
Now, all that said, it's quite possible there is nothing wrong with the drive, it could be the power or SATA cable, or controller causing issues.