Lock washer or not, the ball has to be properly torqued, so as to stretch the shaft to the point where the nut cannot rotate on the threads with less torque applied. The anti-seize was a mistake, torque specifications are almost always for dry threads, adjustments for lube are problematic, but you probably didn't torque it properly anyway.
Use Loctite only if OEM recommended, with the expectation that you will never want to take it apart. Blue Loctite is more easily overcome, but it will take more torque to get it apart than it took to put it together. Consider red Loctite to be almost as permanent as a weld.