We have set up TFS (2015) with a build server and have several solutions that are built (some manually, others automatically).

Sometimes a build will inexplicably fail, with a lot of errors stating that assemblies are missing, like so:

```
The type 'Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

```

To fix it I simply need to queue the build again. No edits, no check-ins, just "queue new build", and it builds successfully.

It can happen on manual builds, on automatic builds, on a single build or when building multiple solutions. I can't see any recognizable pattern to why this happens. I don't think it is a nuget issue, because we see different errors when the build server fails at downloading nuget packages (also, is nuget even used for downloading System.Runtime? I assume that library is readily available on the server?)

As I said, it is easy to fix this, but we're using continous integration and automatic deployment (Octopus) to streamline our release cycle, and these "fake" errors are damn annoying when the build error buzzer starts ringing.