Reproduction steps:
1. Create a new project with the "FPS Microgame" template
2. Open a Script from the project window

Expected result: The code editor is opened without warnings and errors
Actual result: A warning window pops up, multiple errors in the Output window of Visual Studio:
The project file could not be loaded. Could not find file 'E:\\...\\KartGame.csproj'. E:\\...\\KartGame.csproj

Reproducible with: 2.0.14 (2019.4.36f1), 2.0.7, 2.0.11, 2.0.14 (2020.3.27f1)
Not reproducible with: 2.0.5 (2020.3.27f1)
Couldn't test with: 2021.2.10f1, 2022.1.0b6, 2022.2.0a3 (No Microgame templates)

Notes:
1. Not reproducible on an empty project
2. Not reproducible on a URP template
3. Not reproducible after upgrading the project to 2022.2.0a3
4. Tested on Windows
5. Reproduced with Visual Studio 2022 and 2019

Workaround: "Regenerate project files" in "Preferences... > External Tools"