The rear case holds two small plastic covers for the adaptive trigger assembly adjustment sliders. These may have come off during removal. Place them back in the rear cover now to avoid losing them.

Use a pair of tweezers or your fingers to lift the cover from the controller.

Slide the flat end of the cover under the plastic tab in the rear case.

Make sure it is placed so it can move freely in its groove. The edge with the notch should be towards the middle of the controller.

If a cover got bent during the rear case removal or reassembly process, apply a small amount of heat with a hair dryer to restore it to its original shape.

During reassembly, you can use a small piece of painter's tape on the outside of the rear case to hold the covers in place.