If comparator is detecting from a chest placing full block over chest then comparator makes it not detect a chest until blocks are removed and chest opened, if there is a solid block at anypoint on opposite side of chest 1 block higher it will make comparator fail to detect chest opening as a update resulting in need of replacing comparator or making diffrent block update next to it to fix it. Attached screenshot is from server running on paper but it has been tested on pure vanilla and still acted the same even in version 1.20.4