When you run gatsby Develop, and open 5 new pages (in different tabs), everything is going to be normal and fast. But, the subsequent pages opened in new tabs will be suspended, like indefinitely. It will load the first five pages, and the other will be blank, they will work back just when you close one or more, of the previously 5 opened tabs. (edit: as related previously on #12225)
How to Make a Minimal Reproduction: https://www.gatsbyjs.com/contributing/how-to-make-a-reproducible-test-case/
Open, load and work with many new tabs as you want.
New tabs will open but only first 5 are going to working fine, others won't open;
System:
OS: Windows 10 10.0.18363
CPU: (4) x64 Intel(R) Core(TM) i3-9100F CPU @ 3.60GHz
Binaries:
Node: 12.18.3 - C:\Program Files\nodejs\node.EXE
Yarn: 1.22.4 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
npm: 6.14.6 - C:\Program Files\nodejs\npm.CMD
Languages:
Python: 3.8.5 - /c/Users/PICHAU/AppData/Local/Programs/Python/Python38/python
Browsers:
Chrome: 87.0.4280.88
Edge: Spartan (44.18362.449.0)
npmPackages:
gatsby: ^2.21.31 => 2.24.11
gatsby-background-image: ^1.1.1 => 1.1.1
gatsby-cli: ^2.12.106 => 2.12.106
gatsby-image: ^2.4.3 => 2.4.3
gatsby-plugin-google-fonts-v2: 0.0.6 => 0.0.6
gatsby-plugin-manifest: ^2.4.3 => 2.4.3
gatsby-plugin-mdx: ^1.2.7 => 1.2.7
gatsby-plugin-offline: ^3.2.2 => 3.2.2
gatsby-plugin-portal: ^1.0.7 => 1.0.7
gatsby-plugin-react-helmet: ^3.3.1 => 3.3.1
gatsby-plugin-robots-txt: ^1.5.1 => 1.5.1
gatsby-plugin-sharp: ^2.6.3 => 2.6.3
gatsby-plugin-sitemap: ^2.4.11 => 2.4.11
gatsby-plugin-styled-components: ^3.3.1 => 3.3.1
gatsby-remark-images: ^3.3.3 => 3.3.3
gatsby-source-filesystem: ^2.3.3 => 2.3.3
gatsby-transformer-sharp: ^2.5.2 => 2.5.2
npmGlobalPackages:
gatsby-cli: 2.14.1

Duplicate of https://github.com/gatsbyjs/gatsby/issues/12225?
Yes, this is a duplicate of the issue above. Thanks for creating the issue though!