The no-saving part sounds like a bug, but I would need to see a small example workflow demonstrating the behavior. I may also be able to provide a workaround. Have you tried using the try-catch construct yet?
0 2:44:23 FailingNodeStackTrace" (STRING: java.lang.RuntimeException: Cannot read file "<unknown>"
at org.knime.core.data.container.Buffer.iterator(Buffer.java:1653)
at org.knime.core.data.container.ContainerTable.iterator(ContainerTable.java:126)
at org.knime.core.data.container.RearrangeColumnsTable.iterator(RearrangeColumnsTable.java:279)
at org.knime.core.node.BufferedDataTable.iterator(BufferedDataTable.java:317)
at org.knime.core.node.BufferedDataTable.iterator(BufferedDataTable.java:1)
at org.knime.base.data.append.row.AppendedRowsIterator.initNextTable(AppendedRowsIterator.java:326)
at org.knime.base.data.append.row.AppendedRowsIterator.<init>(AppendedRowsIterator.java:156)
at org.knime.base.data.append.row.AppendedRowsTable.iterator(AppendedRowsTable.java:203)
at org.knime.base.node.preproc.append.row.AppendedRowsNodeModel.execute(AppendedRowsNodeModel.java:206)
at org.knime.core.node.NodeModel.execute(NodeModel.java:700)
at org.knime.core.node.NodeModel.executeModel(NodeModel.java:552)
at org.knime.core.node.Node.invokeNodeModelExecute(Node.java:1097)
at org.knime.core.node.Node.execute(Node.java:948)
at org.knime.core.node.workflow.NativeNodeContainer.performExecuteNode(NativeNodeContainer.java:529)
at org.knime.core.node.exec.LocalNodeExecutionJob.mainExecute(LocalNodeExecutionJob.java:95)
at org.knime.core.node.workflow.NodeExecutionJob.internalRun(NodeExecutionJob.java:179)
at org.knime.core.node.workflow.NodeExecutionJob.run(NodeExecutionJob.java:110)
at org.knime.core.util.ThreadUtils$RunnableWithContextImpl.runWithContext(ThreadUtils.java:328)
at org.knime.core.util.ThreadUtils$RunnableWithContext.run(ThreadUtils.java:204)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at org.knime.core.util.ThreadPool$MyFuture.run(ThreadPool.java:120)
at org.knime.core.util.ThreadPool$Worker.run(ThreadPool.java:240)
Caused by: java.io.IOException: Unable to read table from file, table has been cleared.
at org.knime.core.data.container.BufferFromFileIteratorVersion20.<init>(BufferFromFileIteratorVersion20.java:108)
at org.knime.core.data.container.Buffer.iterator(Buffer.java:1641)
... 22 more
) java.lang.RuntimeException: Cannot read file "<unknown>"
at org.knime.core.data.container.Buffer.iterator(Buffer.java:1653)
at org.knime.core.data.container.ContainerTable.iterator(ContainerTable.java:126)
at org.knime.core.data.container.RearrangeColumnsTable.iterator(RearrangeColumnsTable.java:279)
at org.knime.core.node.BufferedDataTable.iterator(BufferedDataTable.java:317)
at org.knime.core.node.BufferedDataTable.iterator(BufferedDataTable.java:1)
at org.knime.base.data.append.row.AppendedRowsIterator.initNextTable(AppendedRowsIterator.java:326)
at org.knime.base.data.append.row.AppendedRowsIterator.<init>(AppendedRowsIterator.java:156)
at org.knime.base.data.append.row.AppendedRowsTable.iterator(AppendedRowsTable.java:203)
at org.knime.base.node.preproc.append.row.AppendedRowsNodeModel.execute(AppendedRowsNodeModel.java:206)
at org.knime.core.node.NodeModel.execute(NodeModel.java:700)
at org.knime.core.node.NodeModel.executeModel(NodeModel.java:552)
at org.knime.core.node.Node.invokeNodeModelExecute(Node.java:1097)
at org.knime.core.node.Node.execute(Node.java:948)
at org.knime.core.node.workflow.NativeNodeContainer.performExecuteNode(NativeNodeContainer.java:529)
at org.knime.core.node.exec.LocalNodeExecutionJob.mainExecute(LocalNodeExecutionJob.java:95)
at org.knime.core.node.workflow.NodeExecutionJob.internalRun(NodeExecutionJob.java:179)
at org.knime.core.node.workflow.NodeExecutionJob.run(NodeExecutionJob.java:110)
at org.knime.core.util.ThreadUtils$RunnableWithContextImpl.runWithContext(ThreadUtils.java:328)
at org.knime.core.util.ThreadUtils$RunnableWithContext.run(ThreadUtils.java:204)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at org.knime.core.util.ThreadPool$MyFuture.run(ThreadPool.java:120)
at org.knime.core.util.ThreadPool$Worker.run(ThreadPool.java:240)
Caused by: java.io.IOException: Unable to read table from file, table has been cleared.
at org.knime.core.data.container.BufferFromFileIteratorVersion20.<init>(BufferFromFileIteratorVersion20.java:108)
at org.knime.core.data.container.Buffer.iterator(Buffer.java:1641)
... 22 more