SourceBrowser: Errors during generation, not sure what's wrong

I’m getting errors on all projects during generation of the site, which in the end contains the projects, but no code.

In the first phase of the generation, each project outputs something similar to this:

10:39:25 21-11-2018 10:39:25: First chance exception
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.CodeAnalysis.MSBuild.ProjectFile.Finalize()
10:39:25 Workspace failed: Msbuild failed when processing the file 'C:\Source\Roadmap\merge2\Apps\Broker\BrokerEndPointService\Nis.Broker.CorePlugin\Nis.Broker.CorePlugin.csproj' with message: Invalid static method invocation syntax: "[Microsoft.Build.Utilities.ToolLocationHelper]::GetPathToStandardLibraries($(TargetFrameworkIdentifier), $(TargetFrameworkVersion), $(TargetFrameworkProfile), $(PlatformTarget), $(TargetFrameworkRootPath), $(TargetFrameworkFallbackSearchPaths))". Method 'Microsoft.Build.Utilities.ToolLocationHelper.GetPathToStandardLibraries' not found. Static method invocation should be of the form: $([FullTypeName]::Method()), e.g. $([System.IO.Path]::Combine(`a`, `b`)).   C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\Bin\Microsoft.Common.CurrentVersion.targets
10:39:25 Msbuild failed when processing the file 'C:\Source\Roadmap\merge2\Apps\Broker\BrokerEndPointService\Nis.Broker.CorePlugin\Nis.Broker.CorePlugin.csproj' with message: Invalid static method invocation syntax: "[Microsoft.Build.Utilities.ToolLocationHelper]::GetPathToStandardLibraries($(TargetFrameworkIdentifier), $(TargetFrameworkVersion), $(TargetFrameworkProfile), $(PlatformTarget), $(TargetFrameworkRootPath), $(TargetFrameworkFallbackSearchPaths))". Method 'Microsoft.Build.Utilities.ToolLocationHelper.GetPathToStandardLibraries' not found. Static method invocation should be of the form: $([FullTypeName]::Method()), e.g. $([System.IO.Path]::Combine(`a`, `b`)).   C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\Bin\Microsoft.Common.CurrentVersion.targets

In the final phase of the generation, each projects outputs this error:

Microsoft.Build.Exceptions.InvalidProjectFileException: Invalid static method invocation syntax: "[Microsoft.Build.Utilities.ToolLocationHelper]::GetPathToStandardLibraries($(TargetFrameworkIdentifier), $(TargetFrameworkVersion), $(TargetFrameworkProfile), $(PlatformTarget), $(TargetFrameworkRootPath), $(TargetFrameworkFallbackSearchPaths))". Method 'Microsoft.Build.Utilities.ToolLocationHelper.GetPathToStandardLibraries' not found. Static method invocation should be of the form: $([FullTypeName]::Method()), e.g. $([System.IO.Path]::Combine(`a`, `b`)).   C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\Bin\Microsoft.Common.CurrentVersion.targets
   at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject(String errorSubCategoryResourceName, IElementLocation elementLocation, String resourceName, Object[] args)
   at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject(IElementLocation elementLocation, String resourceName, Object arg0, Object arg1)
   at Microsoft.Build.Evaluation.Expander`2.Function`1.Execute(Object objectInstance, IPropertyProvider`1 properties, ExpanderOptions options, IElementLocation elementLocation)
   at Microsoft.Build.Evaluation.Expander`2.PropertyExpander`1.ExpandPropertyBody(String propertyBody, Object propertyValue, IPropertyProvider`1 properties, ExpanderOptions options, IElementLocation elementLocation, UsedUninitializedProperties usedUninitializedProperties)
   at Microsoft.Build.Evaluation.Expander`2.PropertyExpander`1.ExpandPropertiesLeaveTypedAndEscaped(String expression, IPropertyProvider`1 properties, ExpanderOptions options, IElementLocation elementLocation, UsedUninitializedProperties usedUninitializedProperties)
   at Microsoft.Build.Evaluation.Expander`2.PropertyExpander`1.ExpandPropertiesLeaveEscaped(String expression, IPropertyProvider`1 properties, ExpanderOptions options, IElementLocation elementLocation, UsedUninitializedProperties usedUninitializedProperties)
   at Microsoft.Build.Evaluation.Expander`2.ExpandIntoStringLeaveEscaped(String expression, ExpanderOptions options, IElementLocation elementLocation)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluatePropertyElement(ProjectPropertyElement propertyElement)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluatePropertyGroupElement(ProjectPropertyGroupElement propertyGroupElement)
   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateImportElement(String directoryOfImportingFile, ProjectImportElement importElement)
   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateImportElement(String directoryOfImportingFile, ProjectImportElement importElement)
   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateImportElement(String directoryOfImportingFile, ProjectImportElement importElement)
   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateImportElement(String directoryOfImportingFile, ProjectImportElement importElement)
   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)
   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate(ILoggingService loggingService, BuildEventContext buildEventContext)
   at Microsoft.Build.Evaluation.Project.Reevaluate(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings)
   at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings)
   at Microsoft.Build.Evaluation.Project.Initialize(IDictionary`2 globalProperties, String toolsVersion, String subToolsetVersion, ProjectLoadSettings loadSettings)
   at Microsoft.Build.Evaluation.Project..ctor(String projectFile, IDictionary`2 globalProperties, String toolsVersion, String subToolsetVersion, ProjectCollection projectCollection, ProjectLoadSettings loadSettings)
   at Microsoft.SourceBrowser.HtmlGenerator.ProjectGenerator.GenerateProjectFile()

It looks like it stems from pretty much the same thing. Any ideas what might be wrong?