Watch opening v5.7 VBP files with v6.0 VBP
 

I just ran into an issue that I opened a 5.7 version file with v6.0 and then I accidently save my changes. The warning is there is NO WARNING message in v6.0 tell me that I am to going to overwrite the format of the file with v6.0.
Then when I realized my mistake v5.7 could no longer open the file.
Why is there no warning message warning you that you are trying to open an older version of a VPB file?

Compatibility issues are documented in the release notes. Of course, it's always a good idea to keep your .bld files in source control so that you can go back to old versions if needed.