When a library (MyLibrary.bib) that was previously saved by a JabRef version X (e.g., an older version) is opened/edited/saved using a different version Y, the backup file MyLibrary.bib.bak previously created by X is overwritten by Y. This may cause a problem if there is an issue with backward compatibility or a bug in Y.
If I remember well, the groups disappeared for some reason when I upgraded last year, possibly from 3.8 to 4.0. After editing/saving with 4.0, the 3.8 backup was overwritten.
I suggest the following:
- When JabRef saves a library, it also saves the JabRef version in it (e.g.,
@Comment{jabref-meta: JabRefVer:4.2;} - When JabRef opens a library and create a backup of it, if the library was previously saved by a different JabRef version (earlier or newer), the name of the backup file should be something like:
MyLibrary-JabRef[OLD_VERSION]-timestamp.bib.bak.
If anything goes wrong due to using a different version, a safe backup is there.