How to reproduce:
1. Open the attached '1296518.zip' project
2. In the Project window double-click on the 'Test' Script
3. Open the Solution Explorer in the Visual Studio (View > Solution Explorer)
4. Open the Error List (View > Error List)
5. In the Solution Explorer expand Assembly-CSharp > References
6. Select any item in the References list
7. Focus on the Script editing area
8. Observe the Error List in the Visual Studio
9. If the issue doesn't reproduce repeat steps 5 to 7 (usually reproduces on the first try, however occasionally it may take up to 3 tries)

Expected result: There are no visible warnings present
Actual result: Warnings appear in the Visual Studio Error List

Reproducible with: 2018.4.30f1, Visual Studio Editor 1.0.2 (2019.4.16f1, 2020.1.17f1, 2020.2.0b14, 2021.1.0a9), 2.0.5 (2020.1.17f1, 2020.2.0b14, 2021.1.0a9)
Cannot test with: Visual Studio Editor 2.0.5 (2019.4.16f1) (the Visual Studio Editor package version is not supported)

Notes:
- Tested with Visual Studio Community 2019 16.8.2
- The character count depends on the Unity version
- In 2018.4 there is no Visual Studio Editor package
- Major part of the warnings are related to referenced components not being found except for the following warning:
'Load of property 'DefineConstants' failed. The argument for the property 'Conditional Compilation Constants' is too long.'