Reproduction steps:
1. Create a new project
2. In the "Assets" folder, create the "StreamingAssets" folder
3. In the "StreamingAssets" folder create a subfolder of any name, but make sure that there's the "" symbol at the end of the name (i.e. "folder")
4. In that folder, create any file of any name (i.e. "file.txt")
5. Build the project by going to "File > Build Settings..." and pressing "Build"
6. After the build is completed, go to "Assets\StreamingAssets\" and delete the previously (in step 3) created subfolder
7. Go back to your project and build it
Expected result: The project builds successfully
Actual result: The project fails to build and the Console error informs that the source path does not exist
Reproduced with: 2021.3.30f1, 2022.3.9f1, 2023.1.12f1, 2023.2.0b8, 2023.3.0a4
Reproduced on: Windows 10 (22H2)
Not reproduced on: No other environments tested