Chinchilla not bonding

I have two chinchillas, McKinley and Copernicus. McKinley and I are really close. He'll curl up in my hand and go to sleep if I put it in the cage during the day, and he loves to sit on my head during playtime. Copernicus, on the other hand, is nowhere near as friendly. After three months, maybe a tiny bit more, of having these two chinchillas (using the standard bonding techniques of the treat in the hand, sit near the cage, etc.) only McKinley made progress. Copernicus doesn't seem afraid of me -- he seems to hate me. He gives me awful glares, makes the kek'ing sound that chinchillas make when fighting while staring at me, and even sometimes attempts to bite me. He takes treats confidently from my hand, as if it's no big deal, but he shows no affection -- only signs of violence and anger. I have done nothing that I can think of to scare him or make him dislike me. He's been like this from day one.

Is it normal for a chinchilla to just act like this? I know it can take a long time to bond, and I don't expect him to be as close to me as McKinley is, but this level of dislike is a bit surprising to me. Has anyone had something like this and know a way to help him get over it?