Unwanted top level OpenGL window & "Error freeing OpenGL context" exceptions


We have an Eclipse-based application that uses VTK 8.2.0 for rendering 3D views in SWT widgets. In some situations an unsolicited window with a title of “Visualization Toolkit - Win32OpenGL #1” opens up and presents a static view of a part of the contents of the scene, while the rest of the contents that are loaded and attached later appear in the SWT widget as intended.

Our views are based on the vtk.rendering.swt.vtkSwtComponent class and no calls to open extra top level windows are made anywhere.

This issues occurs non-deterministically and seems related to multiple VTK views being open at the same time. It is also related to an unhandled GLException when an earlier view is being closed:

!ENTRY org.eclipse.ui 4 0 2020-05-19 15:19:57.346
!MESSAGE Unhandled event loop exception
com.jogamp.opengl.GLException: Error freeing OpenGL context, werr: 6
	at jogamp.opengl.windows.wgl.WindowsWGLContext.releaseImpl(WindowsWGLContext.java:449)
	at jogamp.opengl.GLContextImpl.release(GLContextImpl.java:417)
	at jogamp.opengl.GLContextImpl.release(GLContextImpl.java:382)
	at vtk.rendering.swt.vtkInternalSwtComponent.dispose(vtkInternalSwtComponent.java:128)
	at com.jogamp.opengl.swt.GLCanvas$7.handleEvent(GLCanvas.java:395)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4175)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1081)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1062)
	at org.eclipse.swt.widgets.Widget.release(Widget.java:814)
	at org.eclipse.swt.widgets.Composite.releaseChildren(Composite.java:931)
	at org.eclipse.swt.widgets.Widget.release(Widget.java:817)
	at org.eclipse.swt.widgets.Composite.releaseChildren(Composite.java:931)
	at org.eclipse.swt.widgets.Widget.release(Widget.java:817)
	at org.eclipse.swt.widgets.Widget.dispose(Widget.java:430)
	at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.disposeWidget(SWTPartRenderer.java:175)
	at org.eclipse.e4.ui.workbench.renderers.swt.ContributedPartRenderer.disposeWidget(ContributedPartRenderer.java:273)

Any ideas of what might be the cause of this and where to search? As far as we know, all access to VTK and SWT objects already happens in a single SWT main thread.