Sub-header anchor string reverts to parent header anchor string in URL

[rekmarks]

• I confirm that this is an issue rather than a question.

Bug report

Steps to reproduce

1. Go to https://docs.metamask.io/guide/ethereum-provider.html (although all pages exhibit the same behavior)
2. Click a ### sub-header in the table of contents (e.g. message under Events)
3. Observe the hash in the URL first showing the ### anchor, then reverting to the parent ## anchor

What is expected?

Clicking once on a sub-header should navigate to that sub-header, and its corresponding anchor string should appear and persist in the URL.

What is actually happening?

Clicking once on the sub-header navigates to the sub-header, but the anchor string in the URL reverts to the parent header's anchor string after a few hundred milliseconds.

Click here for recording gif

Other relevant information

• Reproduced in Chrome and Firefox
• Repository: https://github.com/MetaMask/metamask-docs/
• Output of npx vuepress info in my VuePress project:

Environment Info:

  System:
    OS: macOS 10.15.6
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  Binaries:
    Node: 12.18.3 - ~/.nvm/versions/node/v12.18.3/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.6 - ~/.nvm/versions/node/v12.18.3/bin/npm
  Browsers:
    Chrome: 84.0.4147.135
    Edge: Not Found
    Firefox: 79.0
    Safari: 13.1.2
  npmPackages:
    @vuepress/core:  1.5.4
    @vuepress/theme-default:  1.5.4
    vuepress: ^1.5.4 => 1.5.4
  npmGlobalPackages:
    vuepress: Not Found

[rekmarks]

Possibly related anchor shenanigans: #1499, #2489, #2379