diff --git a/src/main/java/com/ffii/fpsms/modules/master/service/ItemsService.kt b/src/main/java/com/ffii/fpsms/modules/master/service/ItemsService.kt
index f59903e..ef6ca46 100644
--- a/src/main/java/com/ffii/fpsms/modules/master/service/ItemsService.kt
+++ b/src/main/java/com/ffii/fpsms/modules/master/service/ItemsService.kt
@@ -450,10 +450,20 @@ open class ItemsService(
             val avg = row["avgUp"] as? BigDecimal ?: return@mapNotNull null
             id to avg.toPlainString()
         }.toMap()
+        // Use JDBC UPDATE instead of load+save: avoids ObjectOptimisticLockingFailureException when the same
+        // Items row was already updated earlier in this transaction (e.g. M18 PO sync) or concurrently.
         idList.forEach { itemId ->
-            val item = itemsRepository.findById(itemId).orElse(null) ?: return@forEach
-            item.averageUnitPrice = avgByItem[itemId]
-            itemsRepository.saveAndFlush(item)
+            val avg = avgByItem[itemId]
+            jdbcDao.executeUpdate(
+                """
+                UPDATE items
+                SET AverageUnitPrice = :avg,
+                    modified = NOW(),
+                    version = version + 1
+                WHERE id = :id AND deleted = 0
+                """.trimIndent(),
+                mapOf("avg" to avg, "id" to itemId),
+            )
         }
     }