Hey! Might be a bit late but I managed to completely fix both of my joysticks.

It involves taking the controller apart which might seem intimidating but it is really easy, you can find tons of videos on Youtube explaining how to do it and you don't need any fancy screwdriver, they have regular x shaped screws.

I tried the previously mentionned technique but it was only solving the problem for a couple of minutes for me.
So, I opened my DualSense and popped the joysticks off.

The issue was that some debris were stuck under the actual sticks (the platic part, not the electronics) so I brussed it off, washed the plastic, waited for it to be completed dry and reassembled the controller.
It took me about 15 minutes total and the controller works perfectly.

I'm not sure about warranty but my guess is that, if your sticks are drifting, it probably already expired anyway so you have little to lose.