This actually failed one evening and I landed flat on my back. I was luckily not hurt but this was unacceptable to my thinking.
So I installed a safety feature. A hand tightened lag screw that prevents the bar from backing off the main bolt. I just remove it to set the chair up, then replace the lag screw to lock the bar down. This mod has made this chair safe and quite securely usable in my opinion was one of two essential modifications. the other was the replacing of the adhesive non-skid strip with the waterproof glued sand on both sides.