Sounds like you are not counterlocking the first threaded nut against the second. By adjusting these two, you get to set tension and lock it in. The rotary shaft turns with the tension you select from that point on. Takes 2 seconds and you won't need to touch it for years.
John, Apples and oranges...
The dynaking kingfisher is not a rotary vise although you can rotate the fly out of concentricity. Wrapping floss bodies for Spey flies is a job best left for the Renzetti. I doubt the super-jaw vises will help lay folded hackles onto french tinsel ribbing. Even palmering a hackle onto a woolly bugger comes out better with a true in-line rotary.
If we're comparing with the $329 Barracuda, that's another story...
Ryan - jaw strength...
I agree that jaw strength is better in Dynaking, Regal and other brands. I use the saltwater renzetti pedastal for stout wire hooks and don't have a problem with the jaws. As the instructions say: adjust the gap with the small thumbscrew so that the hook barely fits thru the gap; then tighten with the big thumbscrew. I am rarely applying enough tension to pull the hook out of position.
That being said, Renzetti should improve the jaw design / strength to remain competitive, I agree - but as far as in-line rotaries go it's design is quite simple compared to some true rotaries on the market - and we should be the ones to get them to do it!