src/de/steamwar/bungeecore/listeners/mods/Fabric.java

@@ -42,6 +42,8 @@ public class Fabric extends BasicListener {
 
     private final Set<String> neededMods = new HashSet<>();
 
+    public static final Set<ProxiedPlayer> checkedPlayers = new HashSet<>();
+
     {
         neededMods.add("java");
         neededMods.add("minecraft");
@@ -108,8 +110,11 @@ public class Fabric extends BasicListener {
         }
 
         if(Utils.handleMods(player,mods)) {
+            if(!checkedPlayers.contains(player)) {
+                Message.send("MODIFICATION_CHECK_SUCCESS", player);
+                checkedPlayers.add(player);
+            }
             Storage.fabricPlayers.remove(player);
-            Message.send("MODIFICATION_CHECK_SUCCESS", player);
         }
     }
 

src/de/steamwar/bungeecore/listeners/mods/ModLoaderBlocker.java

@@ -58,6 +58,7 @@ public class ModLoaderBlocker extends BasicListener {
 
     @EventHandler
     public void onDisconnect(PlayerDisconnectEvent e){
+        Fabric.checkedPlayers.remove(e.getPlayer());
         Storage.fabricPlayers.remove(e.getPlayer());
     }