This ROM is from fans, for fans. Sadly, there are not many developers here. So, if you want a "stable" and fairly recent ROM switch back to the 14.1 release, which I use for nearly two years now without any major problems.
There is a montly build with latest security updates but no further development.
Lets face it: The SM-G800F isn't built for Android O and even N was quite a struggle to get it running. Samsung itself supports only MM. Furthermore, hennymc, the main developer here and owner of the github repository was not very active lately. So I doubt that we will see a "100% stable" 15.1 release in the near future or ever at all.