If the file has already been opened in this version, you need to restore it from the .bak.
Your file has been damaged by a third party element of your computer (most often it is about anti-virus or operating system interferences).
Each time you open your file, the Heredis software creates a copy in .bak format. This copy contains all the information previously entered, but it does not contain the information you have added since the last time you opened the file.
Restoring this copy will allow you to recover most of your data: indeed, only the last data entered will not be recovered.
Here is how to proceed to restore from .bak safely :
Open the software on its home page and click on the cogwheel to the right of the name of the genealogy concerned and select Restore his file from .bak file :