I was working on a layout in VC 5.1 until I realised there’s a bug in it where you cannot set the default product type for assembly slots. Since I still have VC 5.0 installed I thought I would use it to define my assemblies and move on.
However, when I open the file, suddenly half of the layout is missing, except some conveyor rollers and feeders.
I understand no backwards compatibility between 5.x and 4.x, but are 5.x minor versions also going to introduce breaking changes now?
I think the backward compatibility is general, not just between 5.x and 4x.
If there are new functions in 5.1, which didn’t exist in 5.0, you can’t really expect to be able to open a newer layout in an older version and have it work with function which didn’t exist in it yet…
It seems indeed we need to expect backward incompatibility with all version updates of VC 
In this case I was still using 5.0 (didn’t want to upgrade yet due to that assembly step bug) and just evaluating a 5.1 OLP license, so I needed to revert back and got pretty annoyed to see my layout broken.
In general though incompatible changes between major versions is expected - between minor versions it’s surprising. Have a look at https://semver.org/, for example:
- MAJOR version when you make incompatible API changes
- MINOR version when you add functionality in a backward compatible manner
