I think this issue of pathfinding failure due to obstacles might be a bug. I can't figure out how it happens, but I hope that after it's fixed, the search function will work consistently for all such obstructed chests.
This video demonstrates how boxes covered by transparent blocks seem difficult to target, but this problem does not occur on flat ground.
I hope the fix is not simply refusing to recognize these boxes, because there may be cases where the top of the box is blocked by a transparent block but you still want the copper golem to classify it.
This seems to be caused by the top of the box being blocked by a transparent block, such as glass or piston. When it is not blocked, there seems to be no recognition problem.
It is indeed my mistake. When the first box is a large box, the box behind the large box is indeed farther away from the box at the foot, so it is not a bug.