ive replaced my broken left joycon analog stick and now I have issues

Dude im having a very similar issue. I replace the thumb stick and now my trigger isnt working AT ALL. I took it back apart, all the connections are solid, theres no damage, and its still not working. Im ready to throw the joycons through a wall rn. Why the !&&* would nintendo make a controller with this many issues. Its

Did you try calibrating once you replaced the analogue component?

Maybe you’ve got this sorted by now, but the most likely explanation is that one of the ZIF ribbon cables came loose, most likely one of the two that hold the two halves together when you first take out the Y-tip screws and pry the joycon apart.