Workbook either opens as empty (even though there were workflows in it), or with error "Failed to construct a huffman tree using the length array. The stream might be corrupted" (4309656)

In Toad Workbook 5.0 a workbook  is opening up as Blank although there were various workflows within the workbook. 

This is the error if opened with 5.1

System.IO.InvalidDataException Failed to construct a huffman tree using the length array. The stream might be corrupted.

Stack Trace:

at DevExpress.Compression.ZipItem.Extract(Stream stream) at DevExpress.Compression.ZipItem.Extract(String directory, AllowFileOverwriteMode allowFileOverwrite) at Quest.Toad.Util.Compression.UnzipArchive(String zipFile, String outputFilePath, String password, Boolean allowOverwrite) at Quest.WorkflowEngine.WorkflowEngine.DoFileOpen(String file) at Quest.WorkflowEngine.WorkflowEngine.FileOpenAsync(String file)

For unknown reason, the file was corrupted during the save process. Toad saves everything to disk and then the file is zipped. There were some issues during ZIPing the file so this is an irreversible process.