In everyday use the Tekton flex head screw loosens up and falls out even with loctite but that does slow down the process, the end of the handle spreads open over time and I've had to rebuild the ratchet twice in 2 years.
My Snap On FLF80 is 15 years old, has been rebuilt twice by the Snap On driver and had the pin replaced once, works are smothe not clunky, Yes it costs more but it is a better tool.
My favorite locking flex head is still the Matco it the ratchet mechanism is not as robust as the FL80's but the head is thinner it does need a rebuild more often then the Snappy but so far less then the Tekton.