Hey RKH...I've also experienced a few times when the stud lock didn't want to disengage easily. Mostly when the knife was new, and then I discovered that if you twist the stud on it's axis (an off-center or uneven push of the lock as you move it forward toward the tip of the blade), it can be difficult to release. Mine became more tolerable of the twist over time. It's a different locking system, and it does take some getting used to, just like the safety on the flipper.
Work with it for a while, and see if it gets better. This is a great knife for the money, and once accustomed to it, you'll really like it. Hope this helps.............
Oh, and I don't know if you have any other knives with 440A, but you can get this edge wicked sharp. It just takes very light touch-ups more frequently.
SPX