On arrival I noticed that it looked like a return as the inner packaging was already open. The instructions warn that loose connections in a high-current circuit can cause overheating and fire. (It's true!) So I check the screws holding the pre-installed fuse and find that they are both very loose. This was something that wasn't obvious upon viewing and many people probably wouldn't have bothered to check before it overheated and possibly started a fire. Either the factory didn't bother to tighten them, or (more likely given the inner packaging already opened) whoever sent them back fiddled with them and left them loose. This is one of the reasons why businesses should not pass off returned items as new.