Not ground shattering...but could have caused an accident or worse. Checking the bike over before my first ride, I noticed there was a castle nut on the rear brake stabilizer bar, but no cotter pin, and at first, didn't see a hole for the pin in the bolt. Worse, the nut was loose! What had happened was the bolt had a "T" shaped head, and it wasn't seated properly, so the nut couldn't thread on far enough to expose the hole for the cotter pin. If that bar had dropped off when riding....
in earlier days of mechanical ignorance (some say it hasn't changed) I built a custom vespa which has stub axles for both wheels, I didn't know that the cotter pin was necessary and replaced the castellated nuts with whopping great pike nuts, looked great...
a couple of days after I finished the build I was riding out in the country on a club run, I took off quite quickish from the last stop and got up to whatever its claimed top speed was, after a little while the back end started to feel a bit twitchy, shortly followed by the pike nut coming adrift from the stub axle followed shortly afterwards by the back wheel...
the back wheel disappeared up into the body of the scooter, the back of the body hit the ground, tipped over onto its left side and slid towards the side of the road. I was still hanging on at this point but realised that the crash barrier along the freeway was approaching and not wanting to be connected to this large sliding metal thing when it hit, I let go. this however did not stop me from continuing on the same trajectory towards the crash barrier...
I still had time to make one more choice - do I hit the crash barrier upright with my legs apart ...maybe not - do I slide under the crash barrier into the abyss I could see on the other side....maybe not - do I hit the crash barrier upright with on leg ...no time to choose anymore. I hit the upright straight on with the flat of my left foot which forced the ball of my ankle straight up the middle of my tibia
so that didn't end well then