@Bobben_Sun According to the information from our dev team, it's probably because the system running out of memory and failing to save. We will make this as our priority and fix ASAP. Truly sorry for the data you've lost.
@rricktharoolaa Mono will spawn a new individual Mono on contact with water. If you have a sprinkler inside a farm, it's recommended to place walls around it, or build Talisman Flag to prevent mobs from spawning around it. Hope this will help you fix it!