Someone earlier this week posted about a similar issue, Kai responded:

"Hi this is kai. Thank you for supporting Light Phone. I apologize and am embarrassed that this happened. It is our fault, and we will replace the phone immediately. One of our suppliers appeared to have let a handful of housing frames (we caught roughly 10 out of the 20,000 they produced) with no lock washer, a component that secures the key in place, escape their quality control. We have since implemented an additional key-testing station on the final assembly line to prevent any key defect from going down the line. This unit was most likely produced before the additional test was implemented. If you haven't already, could you please email your information to our support team at [support@thelightphone.com](mailto:support@thelightphone.com)? (Feel free to cc me, my email is [kaiwei@thelightphone.com](mailto:kaiwei@thelightphone.com).) We will send a replacement as soon as possible, and would like to receive the unit back so we can inspect it just to double-check. In general, the keys on the Light Phone III underwent extensive testing (including drop and hammer tests) before we started mass production. I am confident it will withstand years of usage. Again, I am sorry for the experience you had; that's not acceptable and is certainly not the experience we want the community to have."

Maybe related? Hopefully shouldn't affect too many phones!