[emily]

This behaviour, in addition to the loud, buzzy-sounding haptics (as demonstrated in the video on my original post) leads me to believe that maybe some of the components are loose. What steps would you recommend I take here?

That one's easy to check, at least: remove the four front screws and look on the back of the faceplate board. The haptic buzzer is this bit, and should be attached to the board. If it's not, it might be hitting the shell of the SD card slot?