My Airpods 2 (with wireless charging case) also clicks when moved side to side whether the lid is opened or closed
So far, I've read several forum posts here and on Reddit about the gen 1 cases and more recently the gen 2 cases exhibiting the same clicking sound when the lid is moved side-to-side.
It's a little annoying and unApple like but from all what I've read, it seems normal.
I passed by the Apple Store and I was told it was normal. Compared it with a unit they had on hand and it clicked as well.
I've read only one instant for each generation of case where the lid didn't click but those might be the ones with issues lol