Fixed #4064

core/src/mindustry/world/blocks/logic/LogicBlock.java

@@ -194,6 +194,7 @@ public class LogicBlock extends Block{
         public LExecutor executor = new LExecutor();
         public float accumulator = 0;
         public Seq<LogicLink> links = new Seq<>();
+        public boolean checkedDuplicates = false;
 
         public void readCompressed(byte[] data, boolean relative){
             DataInputStream stream = new DataInputStream(new InflaterInputStream(new ByteArrayInputStream(data)));
@@ -362,6 +363,21 @@ public class LogicBlock extends Block{
         public void updateTile(){
             executor.team = team;
 
+            if(!checkedDuplicates){
+                checkedDuplicates = true;
+                var removal = new IntSet();
+                var removeLinks = new Seq<LogicLink>();
+                for(var link : links){
+                    var build = world.build(link.x, link.y);
+                    if(build != null){
+                        if(!removal.add(build.id)){
+                            removeLinks.add(link);
+                        }
+                    }
+                }
+                links.removeAll(removeLinks);
+            }
+
             //check for previously invalid links to add after configuration
             boolean changed = false;
 
@@ -371,7 +387,7 @@ public class LogicBlock extends Block{
                 if(!l.active) continue;
 
                 boolean valid = validLink(world.build(l.x, l.y));
-                if(valid != l.valid ){
+                if(valid != l.valid){
                     changed = true;
                     l.valid = valid;
                     if(valid){