Purging shouldn't be main thread, also we have no reason to refresh profiles of purged users, as old users aren't online, and powerless users have nothing to wipe.

src/main/java/com/gmail/nossr50/runnables/database/UserPurgeTask.java

@@ -1,17 +1,22 @@
 package com.gmail.nossr50.runnables.database;
 
+import java.util.concurrent.locks.ReentrantLock;
+
 import org.bukkit.scheduler.BukkitRunnable;
 
 import com.gmail.nossr50.mcMMO;
 import com.gmail.nossr50.config.Config;
 
 public class UserPurgeTask extends BukkitRunnable {
+    private ReentrantLock lock = new ReentrantLock();
     @Override
     public void run() {
+        lock.lock();
         mcMMO.getDatabaseManager().purgePowerlessUsers();
 
         if (Config.getInstance().getOldUsersCutoff() != -1) {
             mcMMO.getDatabaseManager().purgeOldUsers();
         }
+        lock.unlock();
     }
 }