Team Build (XAML) fails with error TF215097

Question

After weeks of normal operation, TFS 2015 XAML builds suddenly fail with error TF215097.

TF215097: An error occurred while initializing a build for build definition \xxxxxxxxxxxxx\xxxxxxxxxxx-DEV: 
Exception Message: A procedure imported by 'Microsoft.VisualBasic.Activities.Compiler.dll' could not be loaded. (type FileLoadException)
Exception Stack Trace:    at Microsoft.VisualBasic.Activities.VisualBasicHelper.CompileT
   at Microsoft.VisualBasic.Activities.VisualBasicHelper.CompileT
   at Microsoft.VisualBasic.Activities.VisualBasicHelper.CompileT
   at Microsoft.VisualBasic.Activities.VisualBasicValue1.CacheMetadata(CodeActivityMetadata metadata)
   at System.Activities.CodeActivity1.OnInternalCacheMetadataExceptResult(Boolean createEmptyBindings)
   at System.Activities.Activity1.OnInternalCacheMetadata(Boolean createEmptyBindings)
   at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList1& validationErrors)
   at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack1& activitiesRemaining, ActivityCallStack parentChain, IList1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)
   at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList1& validationErrors)
   at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList1& validationErrors)
   at System.Activities.Validation.ActivityValidationServices.InternalActivityValidationServices.InternalValidate()
   at Microsoft.TeamFoundation.Build.Workflow.WorkflowHelpers.ValidateWorkflow(Activity activity, ValidationSettings validationSettings)
   at Microsoft.TeamFoundation.Build.Hosting.BuildProcessCache.LoadFromXaml(String workflowXaml, TextExpressionImports textExpressionImports)
   at Microsoft.TeamFoundation.Build.Hosting.BuildControllerWorkflowManager.PrepareRequestForBuild(WorkflowManagerActivity activity, IBuildDetail build, WorkflowRequest request, IDictionary`2 dataContext)
   at Microsoft.TeamFoundation.Build.Hosting.BuildWorkflowManager.TryStartWorkflow(WorkflowRequest request, WorkflowManagerActivity activity, BuildWorkflowInstance& workflowInstance, Exception& error, Boolean& syncLockTaken)

The build definitions themselves and the build activities used haven't changed in the mean time.

The environment is running Visual Studio 2015 update 1, Team Foundation Server 2015 Update 1 on Windows Server 2012r2.

Answer 1

It turns out that this error is caused by the installation of a couple of hotfixes which were delivered through Windows Update. The following KB article explains exactly what the root cause is.

Uninstallation of KB3097997 and KB3098779 and a reboot of the server solved the issue. After the reboot the hotfixes were automatically re-applied without the issue resurfacing.

Thanks to my colleague Jasper for validating :).