If you run the sanity check locally with the `./gradlew sanityCheck`, you can see the binary compatibility error in the output.
It looks like the following:

```
Execution failed for task ':architecture-test:checkBinaryCompatibility'.
> A failure occurred while executing me.champeau.gradle.japicmp.JApiCmpWorkAction
   > Detected binary changes.
         - current: ...
         - baseline: ...