I love my Renzettie Saltwater traveler --- I think it's the best vise tried.[I've tied for 45+years] I haven't had any of the problems you mention. The Jaws seem to consistantly close on the hook.The one thing you might watch for is to put the fly in the jaws the same place/depth each time.
No problem with the shaft turning.
I've had mine a year and tied a lot of flies.
The only thing I've had a problem with is the rubber "O" ring on the back of the jaws----two have broken but just call renzetti and they'll send you a few.
Don't give up on it!!! Good luck!