After a little investigation I discovered that my .c3di file was corrupted. When investigating, I used Windows Explorer and opened the save location and found that the .c3di file in question was about 5% of the size of a previously saved version with a similar number of figures. I assume therefore that during one of the regularly scheduled automatic saves Illustrate crashed. When opening the file Illustrate did not recognize the file as incomplete or corrupted but instead issues the message we've identified here:
"To open the file it must be updated to use a standard. The default standard 'Creo Standard' will be used. Do you want to continue?"
That means to me that the file saved with enough of the structure to allow Illustrate to recognize it but with either many figures lost or elements from the SBOM omitted or links lost leading to loss of figures. It's unclear what exactly gets corrupted but Illustrate's response seems makes it seem like it's a file configuration issue without providing more detail that can be investigated.
My solution is simply to periodically make a copy of the successfully saved .c3di file elsewhere and change the filename to add a time stamp so that a mid-save crash only results in the loss of work completed since the last successful save - once I'm finished making figures I save/upload the very latest version to Windchill. So far this has worked for me as I am the only one accessing the Illustrate files.
