On SERPA holsters in general:
They are affordable, fast, secure, off-set relatively far from the body, and somewhat controversial because of the seeming reality that a certain percentage of users seem to find their trigger fingers inadvertently engaging the trigger immediately upon clearing the holster; a matter of training, ergonomics relative to hand size, possibly both. Note: "Engaging" does not mean to the point of firing; though that's been documented, certainly.
They are also prone to failure under hard use. That's assuming you lock-tighted the screws. You lock-tighted the screws, right? If not, you may not make it to hard use. A bit of searching the net may be in order. Perhaps no other make and model of holster has as much unwanted "press."
As with many things, it may be a case of getting what you pay for.