Well, I fixed the Spigot extremely low spawn rates by moving on higher version - the latest snapshot. We`re playing there 3 days already. Since then there was no server errors / unwanted restarts. Now, we can`t even play more than 5 minutes on our server cause of "Java stack overflow". According to the log, the server "can`t keep up" and closes(without restart).
The world IS NOT corrupted. I downloaded the file and played my server in singleplayer for a hour. Still alive.
And no damn overflows. I searched for the cause of the crashes. Can the lack of RAM reduce the lifespan of the server? We`re so tired of this problems already(