Looks like I killed my ER11 collet nut. You can see some scored metal on its work surface, and the runout is huge and inconsistent. I bought a replacement nut and it works perfectly now.

So, a noob question - how should I take care of my ER11 chucks and collets? Should I lubricate them or keep them dry? How much torque should I apply to the nut? Should the torque be different for small 1/16" collets and big 1/4" collets?