Should I worry about a little wobble at the top of my threaded rods? At worst one of them produces a virtual outside circle of about twice the diameter of the rod. What could be done about that? Is that likely a misalignment of the motor or a problem with the coupler?
Don't try to get rid of that wobble! It's a good thing.
That wobble happens because the threaded rods aren't perfectly straight (none are), and the wobble at the end of the rod doesn't hurt anything. If you try to lock it down with a bearing, as many of the Prusa variants do, the two ends of the rod will be fixed and the wobble will be forced to the center of the rod, where it attached to the X axis. This will cause the layers to be misaligned, resulting in bad prints.