What’s the problem here?

The F4 on this particular instrument was dampened and the 5th was hardly present. Diagnosis, something with the glue in the rim. Next step, sneak my phone in there and investigate. I was correct, uneven glue distribution. Solution? Put a dab of glue on my finger and back fill it. Three hours later it was good as new. I once ran into this issue on a 1rst Gen Hang and had similar success.

In a similar vein, years ago at a handpan festival I had a friend who took his GoPro camera and placed it inside the instrument I was tuning. After we married the clips up for what was like an orthoscopic tuning video.