GL errors in debug mode in slicer (VTK9)

When open_iA is compiled in Debug configuration against VTK9, and when initializing / updating / hovering over the 2D slicer in open_iA, some errors appear in the debug console:
Generic Warning: In C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLState.cxx, line 203
Error in cache state for GL_READ_FRAMEBUFFER_BINDING

Generic Warning: In C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLState.cxx, line 265
at stack loc
 at vtksys::SystemInformationImplementation::GetProgramStack in C:\Tools\vtk\src-9.0.1\Utilities\KWSys\vtksys\SystemInformation.cxx line 3947
 at vtksys::SystemInformation::GetProgramStack in C:\Tools\vtk\src-9.0.1\Utilities\KWSys\vtksys\SystemInformation.cxx line 871
 at vtkOpenGLState::CheckState in C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLState.cxx line 264
 at vtkOpenGLState::vtkBindFramebuffer in C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLState.cxx line 481
 at `anonymous namespace'::FrameBufferHelper::FrameBufferHelper in C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLRenderWindow.cxx line 97
 at vtkOpenGLRenderWindow::GetZbufferData in C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLRenderWindow.cxx line 1616
 at vtkOpenGLRenderWindow::GetZbufferData in C:\Tools\vtk\src-9.0.1\Rendering\OpenGL2\vtkOpenGLRenderWindow.cxx line 1692
 at vtkRenderer::GetZ in C:\Tools\vtk\src-9.0.1\Rendering\Core\vtkRenderer.cxx line 1346
 at vtkWorldPointPicker::Pick in C:\Tools\vtk\src-9.0.1\Rendering\Core\vtkWorldPointPicker.cxx line 47
 at iASlicer::updatePosition in C:\Tools\iAnalyse\src\open_iA\core\src\iASlicer.cpp line 1372
 at iASlicer::execute in C:\Tools\iAnalyse\src\open_iA\core\src\iASlicer.cpp line 1312
 at iAObserverRedirect::Execute in C:\Tools\iAnalyse\src\open_iA\core\src\iASlicer.cpp line 236
 at vtkSubjectHelper::InvokeEvent in C:\Tools\vtk\src-9.0.1\Common\Core\vtkObject.cxx line 629
 at vtkObject::InvokeEvent in C:\Tools\vtk\src-9.0.1\Common\Core\vtkObject.cxx line 795
 at QVTKInteractorAdapter::ProcessEvent in C:\Tools\vtk\src-9.0.1\GUISupport\Qt\QVTKInteractorAdapter.cxx line 136
 at QVTKRenderWindowAdapter::handleEvent in C:\Tools\vtk\src-9.0.1\GUISupport\Qt\QVTKRenderWindowAdapter.cxx line 706
 at QVTKOpenGLNativeWidget::event in C:\Tools\vtk\src-9.0.1\GUISupport\Qt\QVTKOpenGLNativeWidget.cxx line 271
 at QMdiArea::viewMode
 at QMdiArea::viewMode
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QMdiArea::viewMode
 at QMdiArea::viewMode
 at QMdiArea::viewMode
 at QMdiArea::viewMode
 at QMdiArea::viewMode
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QOpenGLFunctions::glDeleteShader
 at QOpenGLFunctions::glDeleteShader
 at QOpenGLFunctions::glDeleteShader
 at qt_plugin_instance
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at qt_plugin_instance
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QAbstractFileEngineHandler::~QAbstractFileEngineHandler
 at QOpenGLFunctions::glDeleteShader
 at QMdiArea::viewMode
 at MainWindow::runGUI in C:\Tools\iAnalyse\src\open_iA\core\src\mainwindow.cpp line 2578
 at main in C:\Tools\iAnalyse\src\gui\main.cpp line 6
 at WinMain in C:\Users\qt\work\qt\qtbase\src\winmain\qtmain_win.cpp line 97
 at invoke_main in d:\A01\_work\6\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl line 107
 at __scrt_common_main_seh in d:\A01\_work\6\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl line 288
 at __scrt_common_main in d:\A01\_work\6\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl line 331
 at WinMainCRTStartup in d:\A01\_work\6\s\src\vctools\crt\vcstartup\src\startup\exe_winmain.cpp line 17
 at BaseThreadInitThunk
 at RtlUserThreadStart
3dct / open_iA

GL errors in debug mode in slicer (VTK9) #54
