I used pocket screws to build boxes for my kitchen cabinets out of 3/4” plywood. While I had a bit of a learning curve at first driving the screws without pulling the joint out of perfect alignment, the screws definitely provided a solid connection. Based on your description, the only thing that comes to mind is to be sure you use the set up block to get the collar on the drill bit set at the proper depth for the length of screw you are using. There is not a lot of wiggle room to work with. (I have the K5, but assume the K4 works the same way.)