Sporadic issue restoring F# packages

We have a customer that, upon package load, occassionally gets this error in one of his functions:

```
2017-05-10T14:16:12.594 Script for function 'my-function' changed. Reloading.
2017-05-10T14:16:21.080 Package restore failed:
2017-05-10T14:16:21.534 System.Reflection.ReflectionTypeLoadException : Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
at System.Reflection.RuntimeModule.GetTypes(RuntimeModule module)
at System.Reflection.RuntimeModule.GetTypes()
at System.Reflection.Assembly.GetTypes()
at Microsoft.Azure.WebJobs.Script.Description.FSharpCompilation.GetEntryPointSignature(IFunctionEntryPointResolver entryPointResolver)
at async Microsoft.Azure.WebJobs.Script.Description.DotNetFunctionInvoker.ReloadScriptAsync()
at async Microsoft.Azure.WebJobs.Script.FuncExtensions.<>c__DisplayClass0_0`1.b__0[T](??)
at async Microsoft.Azure.WebJobs.Script.Description.DotNetFunctionInvoker.RestorePackagesAsync(Boolean reloadScriptOnSuccess)
```

The HttpTrigger returns a 404 whenever this happens. This doesn't happen every time -- when it loads correctly, everything runs fine.