I’d pull the whole thing apart. You’d be surprised what gunk I’ve found under buttons. Usually spilt drinks, nicotine, caustic leaked battery fluid, coca cola .
I’ve fixed lots of remotes rendered “dead” from leaking batteries ( Duracell be damned ) . They always come back to life after a good clean
white vinegar to remove the caustic battery sludge from the battery contacts and pcb board then isopropyl alcohol to remove the vinegar
then put eveready...