I've used Blade Tech IWB holsters pretty much daily for close to 15 years now. As was mentioned, the retaining screws can be adjusted till you about rip your pants off trying to get the gun out.
I tried a couple of thumb breaks when I first started carrying and soon cut them off. I think they are more annoying and more of a hazard than anything else.
Try setting the tension so it takes a little effort from a slow pull. It should slip smoothly out with a firm draw. With the gun in the holster, do a slow, backwards roll onto your shoulders so your upside down and give some hard shakes. The gun shouldnt, and most likely wont, come out.