I owned a pair of the first gen AirPods Max. After a couple of months of usage, I began noticing a rattling inside the right earcup. I had never dropped them or exposed them to any sort of physical damage that could knock something loose. The rattling would happen every time I tilted my head in any direction. I had taken them to Apple Genius support in store 3 different times and 2 of those times the onsite tech agreed that there was a rattling sound. All 3 times they were sent to an Apple repair facility and they always came back with "cannot reproduce". I sold them on FB Marketplace for a deep discount, having alerted the potential buyer to the issue before I sold them to him. Never again will I purchase a set of AirPods.
I sent them to support with a very good description of the problem, came back the same, “cannot reproduce”.
It seems support workers for both companies just connect them to an audio source and check if sound comes out relatively alright.