I Can’t Properly Control My DJI RC N3 Due to a Loose Vertical Axis Screw

I’m currently having a serious issue with my DJI RC N3 controller. The up/down (vertical) control stick isn’t working as it should because the screw inside the mechanism has loosened. As a result, when I push the stick up, the drone only responds at about 80% power, making vertical lift slow and inconsistent.

I live in Demre, Antalya, and unfortunately, there’s no nearby DJI-authorized service center. I want to fix this myself, but I need clear guidance.
Which type of screwdriver should I use to access and tighten the control axis? Is there a specific method or tool DJI recommends for tightening or adjusting the internal screw?

Please assist me as soon as possible. This issue is making the drone difficult and unsafe to fly, and I’d prefer to resolve it without having to ship the controller elsewhere.