overlapped links become inaccessible in Sankey plot

Hi,
I figured out that in Sankey diagram, if the links overlap, sometimes certain links go in the background and become inaccessible. Here is my codepen for the reported case: (https://codepen.io/mateo-forjan/pen/NWZWyPd).

Trying to access link info for links 1->4 and 2->4 is impossible from the inside of the link 3->4 because it seems those are in the background of the mentioned link. Sometimes, there can be a situation where one link from the background can be accessed and another one cannot.

首先在 Sankey 图中复现链接的重叠情形，该情形来自链接的 CodePen。然后跟踪 Sankey 链接交互或命中测试的入口点，并确定链接 1→4、2→4 和 3→4 是如何分层的。完成的标准是每个重叠链接都可以访问并检查其信息；该 issue 没有指定任何仓库文件或要运行的测试。