[INFO] Chunk (42, -2) stored at (35, -28)
[SEVERE] at org.bukkit.craftbukkit.util.LongHashtable.get(LongHashtable.java:32)
[SEVERE] at net.minecraft.server.ChunkProviderServer.getOrCreateChunk(ChunkProviderServer.java:104)
[SEVERE] at net.minecraft.server.World.getChunkAt(World.java:300)
[SEVERE] at net.minecraft.server.World.getTypeId(World.java:247)
The above is what chunk corruption errors look like. Chunk corruption can cause a plethora of problems including: lag, world data not saving, world holes, malfunctioning plugins, and other odd behavior. There aren't many solutions to fixing it other than by using a program such as MCEdit to remove the damaged area or using chunk repair utilities (if they are not outdated/still in development).