Compilation failure due to 'maximum number of concurrent builds reached'?

Hi guys,

As in the title, I get an error of compilation with the error message reads: ‘Maximum number of concurrent builds reached’.

I don’t know why, and what are these concurrent multiple builds are being accumulating in the first place.

The version of unreal is UE4.27, and the version of Visual Studio is VS2022.

One piece of information, the engine is downloaded to the D: \ drive and not to the C: \ drive. And so is the project itself. Another piece of information, the editor did compile normally many times before, and did fail as well before. It is not a sudden thing.