You have found out why I always recommend people buy the best vise they can afford. And if they can't afford it at the time, put money away for 6 months and then get the top end vise. To do otherwise is false economy if you are tying a lot of flies or very large flies.
The two best vises on the market bar none are the Renzetti Master Vise (getting really close the $600.00 US) or my favorite vise the Dyna King Barracuda (around $330.00 US), which is also available in a 3/4 size model called the Barracuda Jr (around $285.00 US). The other vises on the market just don't do what these two very finely crafted vises will do. Dyna King makes a superb vise for around $250.00 US as well which is not a true rotary because it doesn't have the angled vise arm; however, it has hook holding that is every bit the equal of the Barracuda.
The Renzetti Traveler (whether saltwater or standard) is OK for lighter duty tying or for flies of #2 and smaller; however, neither one was designed for volumn tying or for tying the really large stuff. I would take a file to the thimb screw though as John suggested, it makes a world of difference and is something that I tell people to do as a matter of course with the Renzetti Travelers.