I noticed my 2&5/16" ball on my WD hitch was about a 1/4 turn loose today. It had about 4000 heavy miles on it. Even with the lock washer it was able to back off a little over time. I use a 3' pipe wrench to tighten it back up to spec which is over 250ft lbs. I also keep an eye on the hitch platform bolts as well.