Chosen Solution
I had a really bad up/left drift problem on my left joycon, so I ordered the repair kit and followed the guide. After replacing the stick it now has a slight downward drift problem, noticeable in calibration and while playing a game (tested game was Animal Crossing New Horizons, the character would slowly move downward when the stick was not being touched)
Make sure the ribbon cable and the connector for the joystick is clean. Contaminants there can sometimes cause drift
Did you try updating controllers? It worked for me
As well as the 2 answers above you can also try re calibarating the joy con and lastly reset the console by holding down the power button for 10-12 seconds. Usually the 4 things mentioned here combined will sort it out. Changed about 5 sets so far and no issues now EDIT Sorry didn’t fully read your question seems you did calibarate it already. So it could be the housing around the joystick has become dislodged. You cant also rule out that the replacement stick is just faulty. Usually in those kits you get 2 or 3 sticks so try another.
