ItemNotFoundException when editing document with picture in HTML field

Unfortunately, I've not been able to find a reliable reproduction path. When creating & editing documents, adding & removing images, sometimes the document does not open when clicking "edit", instead showing a stacktrace [I've removed the numerous AccessDeniedExceptions that seem to be unrelated]:

20.01.2009 13:36:30 ERROR [org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin.execute():231] Invalid data to save
javax.jcr.ItemNotFoundException: HierarchyEntry does not belong the given ItemInfo.
at org.apache.jackrabbit.jcr2spi.state.WorkspaceItemStateFactory.assertMatchingPath(WorkspaceItemStateFactory.java:475)
at org.apache.jackrabbit.jcr2spi.state.WorkspaceItemStateFactory.assertValidState(WorkspaceItemStateFactory.java:457)
at org.apache.jackrabbit.jcr2spi.state.WorkspaceItemStateFactory.createItemStates(WorkspaceItemStateFactory.java:215)
at org.apache.jackrabbit.jcr2spi.state.WorkspaceItemStateFactory.createDeepNodeState(WorkspaceItemStateFactory.java:116)
at org.apache.jackrabbit.jcr2spi.state.TransientISFactory.createDeepNodeState(TransientISFactory.java:108)
at org.apache.jackrabbit.jcr2spi.hierarchy.UniqueIdResolver.resolve(UniqueIdResolver.java:73)
at org.apache.jackrabbit.jcr2spi.hierarchy.HierarchyManagerImpl.getNodeEntry(HierarchyManagerImpl.java:104)
at org.apache.jackrabbit.jcr2spi.SessionImpl.getNodeById(SessionImpl.java:250)
at org.apache.jackrabbit.jcr2spi.SessionImpl.getNodeByUUID(SessionImpl.java:223)
at org.hippoecm.repository.decorating.SessionDecorator.getNodeByUUID(SessionDecorator.java:165)
at org.hippoecm.frontend.plugins.reviewedactions.FullReviewedActionsWorkflowPlugin$2.execute(FullReviewedActionsWorkflowPlugin.java:94)
at org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin.execute(AbstractWorkflowPlugin.java:222)
at org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin.access$000(AbstractWorkflowPlugin.java:52)
at org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin$2.onClick(AbstractWorkflowPlugin.java:143)
at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:65)