Link in title throws an error

[itmayziii]

System:
OS: macOS 10.15.4
CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Shell: 5.7.1 - /bin/zsh
Binaries:
Node: 12.16.1 - /usr/local/bin/node
npm: 6.14.5 - /usr/local/bin/npm
Languages:
Python: 2.7.16 - /usr/bin/python
Browsers:
Chrome: 83.0.4103.97
Firefox: 75.0
Safari: 13.1
npmPackages:
gatsby: ^2.18.10 => 2.18.10
gatsby-link: ^2.2.27 => 2.2.27
gatsby-plugin-algolia: ^0.5.0 => 0.5.0
gatsby-plugin-emotion: ^4.1.18 => 4.1.18
gatsby-plugin-gtag: ^1.0.12 => 1.0.12
gatsby-plugin-layout: ^1.1.18 => 1.1.18
gatsby-plugin-manifest: ^2.2.33 => 2.2.33
gatsby-plugin-mdx: ^1.0.61 => 1.0.61
gatsby-plugin-offline: ^3.0.29 => 3.0.29
gatsby-plugin-react-helmet: ^3.1.18 => 3.1.18
gatsby-plugin-remove-serviceworker: ^1.0.0 => 1.0.0
gatsby-plugin-remove-trailing-slashes: ^2.1.17 => 2.1.17
gatsby-plugin-sharp: ^2.3.7 => 2.3.7
gatsby-plugin-sitemap: ^2.2.24 => 2.2.24
gatsby-remark-copy-linked-files: ^2.1.33 => 2.1.33
gatsby-remark-images: ^3.1.37 => 3.1.37
gatsby-source-filesystem: ^2.1.42 => 2.1.42
gatsby-transformer-remark: ^2.6.42 => 2.6.42
npmGlobalPackages:
gatsby-cli: 2.12.44
gatsby: 2.23.1

[stellakunzang]

I was having a similar problem recently, and perhaps my findings will help you. It seems that when putting a link in a header it tries to assign this as the id for that header, but the header already has an id. This was the cause of my error at least, and the solve was to move the link outside of a header 🤷‍♀️