diff --git a/app/src/Lib/Events/RuleBuilderEventListener.php b/app/src/Lib/Events/RuleBuilderEventListener.php
index 7dd427fb0..9d5451512 100644
--- a/app/src/Lib/Events/RuleBuilderEventListener.php
+++ b/app/src/Lib/Events/RuleBuilderEventListener.php
@@ -39,6 +39,16 @@
 
 class RuleBuilderEventListener Implements EventListenerInterface {
   use \App\Lib\Traits\LabeledLogTrait;
+
+  /**
+   * Track which RulesChecker instances we've already modified, to avoid adding
+   * duplicate rules (which can trigger duplicate rule-name exceptions).
+   *
+   * Key format: "<TableAlias>#<spl_object_id(RulesChecker)>"
+   *
+   * @var array<string, bool>
+   */
+  private static array $buildRulesRan = [];
   
   /**
    * Build rules event listener.
@@ -69,6 +79,14 @@ public function buildRules(Event $event, RulesChecker $rules) {
 
     }
 
+    $onceKey = $subjectTable->getRegistryAlias() . '#' . spl_object_id($rules);
+    if (isset(self::$buildRulesRan[$onceKey])) {
+      // Already built rules for this table+rules checker; avoid duplicate rule-name exceptions.
+      $event->setResult($rules);
+      return;
+    }
+    self::$buildRulesRan[$onceKey] = true;
+
     $schema = $subjectTable->getSchema();
     
     // We need to skip some metadata fields, including changelog and EIS fks