I have a similar issue with my cheap tws earbuds. What i ended up doing was cleaning up the metal contacts on both the earbuds and the case. And whenever i place my earbuds in my case i give it a little wiggle just to make sure the metal contacts are actually touching. I have no clue if this will help or whether pixel buds even have such metal contacts but you can try.
I have a similar issue with my cheap tws earbuds. What i ended up doing was cleaning up the metal contacts on both the earbuds and the case. And whenever i place my earbuds in my case i give it a little wiggle just to make sure the metal contacts are actually touching. I have no clue if this will help or whether pixel buds even have such metal contacts but you can try.