Mikereidis, the original developer, stopped development around 2017 after Google removed the necessary APIs and phone manufacturers began omitting FM chips to push streaming services. The source code was never fully open-sourced. The "fixed" versions are reverse-engineered patches from the Android modding community.
For a frustration-free experience, root your phone (if possible). On Samsung US variants (locked bootloaders), rooting is impossible, so the fixed APK may be limited to basic analog tuning.