Force imported attributes id to be lowercase

app/code/community/Pimgento/Api/Helper/Entities.php

@@ -201,4 +201,27 @@ public function getColumnsFromResult(array $result)
 
         return (array)$columns;
     }
+
+    /**
+     * Set key to lower case
+     * to avoid problems with values import
+     *
+     * @param string $key
+     *
+     * @return string
+     */
+    public function keyToLowerCase($key)
+    {
+        /** @var string[] $keyParts */
+        $keyParts    = explode('-', $key, 2);
+        $keyParts[0] = strtolower($keyParts[0]);
+        /** @var string $newKey */
+        if (count($keyParts) > 1) {
+            $newKey = $keyParts[0].'-'.$keyParts[1];
+        } else {
+            $newKey = $keyParts[0];
+        }
+
+        return $newKey;
+    }
 }

app/code/community/Pimgento/Api/Helper/Family/Variant.php

@@ -35,6 +35,7 @@ public function getColumnsFromResult(array $result)
          * @var mixed  $value
          */
         foreach ($result as $key => $value) {
+            $key = $this->keyToLowerCase($key);
             if (in_array($key, static::EXCLUDED_COLUMNS)) {
                 continue;
             }

app/code/community/Pimgento/Api/Helper/Product.php

@@ -47,6 +47,7 @@ public function getColumnsFromResult(array $result)
          * @var mixed  $value
          */
         foreach ($result as $key => $value) {
+            $key = $this->keyToLowerCase($key);
             if (in_array($key, static::EXCLUDED_COLUMNS)) {
                 continue;
             }