Why does my controller still have stick drift?

A few months ago my black dual sense controller developed downward stick drift. I sprayed the joysticks with some air to try and clean it, and reset the controller with the button on the back and the drift persisted. I finally ordered some replacement sticks from amazon. The replacements I ordered were (EL6-ALPS-2.1K) and, according to the box, were manufactured by Yuyaohengzhou. First I replaced the entire left and right joysticks, not just the potentiometers, and the drift persisted. I then replaced just the potentiometers, and the drift persisted. Finally, I cleaned inside the potentiometer housing with isopropyl alcohol. The drift is still there and I’m running out of options. What else could be causing the stick drift even after all that?