Cause of Eclipse Neon.3 crash? - eclipse

Question

My Eclipse Neon.3 keeps crashing while I'm editing, requiring me to exit and restart it. I submitted an Eclipse automatic report, but it was auto closed with the result "3rd party caused AssertionFailedException below HandlerServiceImpl.executeHandler"
Does that mean additionally installed software (plugin?) caused it?
I cannot figure out what could be causing it from the stack trace, below (from the ticket) and I don't see anything named like any installed software.
How can I decode this to determine what is causing this repeated crash?
org.eclipse.core.runtime.AssertionFailedException: --- message available to reviewers only ---
at org.eclipse.core.runtime.Assert.isTrue(Assert.java:110)
at org.eclipse.core.runtime.Assert.isTrue(Assert.java:96)
at org.eclipse.jface.text.Position.setLength(Position.java:185)
at HIDDEN.HIDDEN(HIDDEN:0)
at org.eclipse.core.commands.Command.firePostExecuteSuccess(Command.java:665)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:495)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:486)
at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:210)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.executeCommand(KeyBindingDispatcher.java:286)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.press(KeyBindingDispatcher.java:507)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.processKeyEvent(KeyBindingDispatcher.java:558)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.filterKeySequenceBindings(KeyBindingDispatcher.java:378)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.access$0(KeyBindingDispatcher.java:324)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher$KeyDownFilter.handleEvent(KeyBindingDispatcher.java:86)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.filterEvent(Display.java:1550)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1328)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1353)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1338)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1365)
at org.eclipse.swt.widgets.Widget.gtk_key_press_event(Widget.java:763)
at org.eclipse.swt.widgets.Control.gtk_key_press_event(Control.java:3317)
at org.eclipse.swt.widgets.Composite.gtk_key_press_event(Composite.java:785)
at org.eclipse.swt.widgets.Tree.gtk_key_press_event(Tree.java:1895)
at org.eclipse.swt.widgets.Widget.windowProc(Widget.java:1980)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:5590)
at org.eclipse.swt.widgets.Tree.windowProc(Tree.java:3612)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:4717)
at org.eclipse.swt.internal.gtk.OS._gtk_main_do_event(OS.java:-2)
at org.eclipse.swt.internal.gtk.OS.gtk_main_do_event(OS.java:9279)
at org.eclipse.swt.widgets.Display.eventProc(Display.java:1225)
at org.eclipse.swt.internal.gtk.OS._g_main_context_iteration(OS.java:-2)
at org.eclipse.swt.internal.gtk.OS.g_main_context_iteration(OS.java:2425)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3428)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1127)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1018)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:156)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:654)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:598)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:139)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:380)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:235)
at HIDDEN.HIDDEN(HIDDEN:0)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:669)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:608)
at org.eclipse.equinox.launcher.Main.run(Main.java:1515)
at org.eclipse.equinox.launcher.Main.main(Main.java:1488)