The 50lb on the spindle nut is to seat the races after a new install. You don't need to tighten that much on subsequent service. A firm tighten with pliers will displace excess grease. After the tightening, you back off till it is completely loose without turning the wheel. Then finger tight and back off to first place the cotter/lock can be installed. You want just a very small amount of clearance.
I suspect that you have the wrong bearings or the races are cocked. Are the spindles damaged?
The wires on the magnets are colored for identification. Always use the original color. Perhaps the magnets are grabbing, without being energized, by getting wedged in some way.
