When you place two chests next to each other, the resulting large chest has an unclickable "seam" in the middle where the two small chests are joined. You can see from the screenshots that when I have my cursor slightly to the left or right of center, the chest bounding box is visible, but when it is over the middle region the bounding box disappears. In that condition, right-click will not open the chest.

I run into this a lot because I automatically go for the latch when opening chests and somehow manage to hit the dead area most of the time.