Like any snapshot tester, please file an issue on GitHub. As you know, snapshot builds are not expected to be fully functional. They are designed to find issues such as this but it needs to be reported where it can be resolved.
What is your persistence? Is it running? Is is set in PaperUI --> Configuration --> System --> Persistence --> Default Service? If there is your correct entry? You should try: remove it, save empty, fill it in again, save again.