Answer to "My left analog stick is not moving properly...?"I had a number of difficulties with left thumbstick registering incorrectly, and I found that the following steps helped immensely: Rotate the stick around a bunch CLICK the stick down and while holding it down, rotate again Keeping the stick clicked in, move it downward and blow air into the gap at the top Put the stick upward and blow into the bottom area Rotate the stick again, both unpressed and pressed Blow air all around the inside with the stick clicked down Release the stick and give the controller a few firm whacks Click the stick back in and blow around the edges again Reset the controller using the reset pinhole button for good measure, and then test after reconnecting to the PS4. All my problems seemed to be caused by dirt creeping in while I was sprinting in some game, holding the stick down and forward. Merely blowing some air in didn’t help, the constant agitation and blowing and repeating seemed to be the only thing to clean it out without opening the device (which is a fair degree harder...
Answer to "Face buttons are loose"This isn't a particularly good answer, as I haven't had the chance to open a DS4 yet, but I can almost guarantee that something fell out or was misplaced when you replaced your joysticks, typically a lot of components are sitting loose in the enclosure, especially face buttons. If you don't get an answer that's a bit more helpful, try opening the controller in question as well as another controller that hasn't been opened, see if there's any discrepancies. Just make sure to keep the front of the controller facing down so none of the buttons or anything fall out, I think that's mentioned in the joystick replacement guide as well.