Pro Controller Joystick Replacement

Hey, guys! Currently have a question on some joysticks I bought for the Nintendo Switch Pro Controller. I bought them a few weeks ago on eBay and upon arrival and further inspection, I noticed the stick joystick was getting stuck in position I moved it in and it didn’t return to the center unless I would pull it back myself. I didn’t think much of them because they were advertised as OEM, so when I messaged the seller asking if this was normal, he advised it was because they need to be properly calibrated. I’m completely unaware of how that works so I was maybe hoping someone could help me figure this out.

Thanks in advance.

If the stick itself gets stuck on the outer postion and doesn’t return to the middle, it maybe a problem with the heights of the thumbstick on the stick or the the stick modul itself.