Since my server updated to Minecraft 20w17a we have been experiencing issues in which raids spawn underground within caves at our raid farm. From my knowledge raids are only supposed to spawn in areas in which they have contact with direct sunlight (no roof) which is the main premise of our farm, however within this snapshot I have noticed in spectator mode raids spawn in caves underground.
Worlds opened in 20w17a are broken and need to be repaired manually. Please check whether the fix from MC-179845 solves this issue.