Please note the .au files need to be numbered consecutively when input to the Crash Recovery Utility or errors will occur in the program. If this problem occurs you can open Audacity's temporary folder in your system File Manager (e.g., Windows Explorer) and try resorting the .au files by time modified and then batch renaming them using a numeric sequence whilst they are sorted by time modified. An arrangement looking something like this should work:
- b001.au 15:56:02
- b002.au 15:56:02
- b003.au 15:56:10
- b004.au 15:56:10
If your file manager does not have a suitable renaming tool, you should be able to obtain suitable free tools on the Internet.