Are you using special characters, like €, in attribute, feature type or transformer names?

What you can try is open the .fmw file in a text editor and search for that character, then replace it with something that's not a special character. Make sure to save it under a different name though! Then try open that in Workbench.

Can you maybe create a support case and send the workspace file to us? If FME created a file we ought to be able to open it again. I think we'd also be interested to know what locale your computer is using.

Unfortunately, I didn’t keep the corrupted file. However, this is the first time ever I got an fme file corrupted.

The message is irrelevant as I didn’t use the symbol indicated