Chosen Solution

The headphones still work but the side with power button/lights is coming apart. I’m not sure how this has happened or how to fix it. I’ve tried clicking the parts back in place but the parts won’t stay together

I had this issue too. The screws that hold the casing down screw into threads that are mounted into plastic houses. These plastic houses seem to shear off easily which then releases the threads and the screws have nothing to screw into.

Yellow circle is how it should look Red circle is a broken housing If you are lucky all your screws and threads are still rattling around in your headphones. You can take the casing off, reattach the threads (some surgu or similar will help if there is not enough housing to affix to - I was lucky and could just glue the threads back on). Reattach the casing, put the screws back in and viola! This video is helpful for getting the casing off https://m.youtube.com/watch?v=9jm6KkTYxd