diff --git a/packages/components/credentials/GoogleSheetsOAuth2.credential.ts b/packages/components/credentials/GoogleSheetsOAuth2.credential.ts
index 3e21479224f..259bfc31747 100644
--- a/packages/components/credentials/GoogleSheetsOAuth2.credential.ts
+++ b/packages/components/credentials/GoogleSheetsOAuth2.credential.ts
@@ -1,5 +1,6 @@
 import { INodeParams, INodeCredential } from '../src/Interface'
 const scopes = [
+    'https://www.googleapis.com/auth/drive',
     'https://www.googleapis.com/auth/drive.file',
     'https://www.googleapis.com/auth/spreadsheets',
     'https://www.googleapis.com/auth/drive.metadata'
diff --git a/packages/ui/src/views/docstore/LoaderConfigPreviewChunks.jsx b/packages/ui/src/views/docstore/LoaderConfigPreviewChunks.jsx
index 660571ff358..f32fa7179ad 100644
--- a/packages/ui/src/views/docstore/LoaderConfigPreviewChunks.jsx
+++ b/packages/ui/src/views/docstore/LoaderConfigPreviewChunks.jsx
@@ -31,7 +31,7 @@ import documentStoreApi from '@/api/documentstore'
 import documentsApi from '@/api/documentstore'
 
 // Const
-import { baseURL, gridSpacing } from '@/store/constant'
+import { baseURL, gridSpacing, FLOWISE_CREDENTIAL_ID } from '@/store/constant'
 import { closeSnackbar as closeSnackbarAction, enqueueSnackbar as enqueueSnackbarAction } from '@/store/actions'
 import { useError } from '@/store/context/ErrorContext'
 
@@ -147,7 +147,7 @@ const LoaderConfigPreviewChunks = () => {
                 if (
                     inputParam.type === 'credential' &&
                     !selectedDocumentLoader.credential &&
-                    !selectedDocumentLoader.inputs['FLOWISE_CREDENTIAL_ID']
+                    !selectedDocumentLoader.inputs[FLOWISE_CREDENTIAL_ID]
                 ) {
                     canSubmit = false
                     missingFields.push(inputParam.label || inputParam.name)
@@ -317,6 +317,18 @@ const LoaderConfigPreviewChunks = () => {
                 nodeData.credential = existingLoaderFromDocStoreTable.credential
                 setLoaderName(existingLoaderFromDocStoreTable.loaderName)
             }
+            // Restore credential from the separate `credential` field on the loader entity.
+            // This block intentionally runs outside the loaderConfig guard above because
+            // `loader.credential` is persisted as its own DB column — independent of
+            // loaderConfig — and may be the *only* place the credential ID is stored for
+            // loaders created before FLOWISE_CREDENTIAL_ID was written into inputs.
+            // Without this, checkMandatoryFields and prepareConfig both miss the credential,
+            // causing a false "Connect Credential" validation error on process/preview.
+            if (existingLoaderFromDocStoreTable?.credential) {
+                nodeData.credential = existingLoaderFromDocStoreTable.credential
+                if (!nodeData.inputs) nodeData.inputs = {}
+                nodeData.inputs[FLOWISE_CREDENTIAL_ID] = existingLoaderFromDocStoreTable.credential
+            }
             setSelectedDocumentLoader(nodeData)
 
             // Check if the loader has a text splitter, if yes, get the text splitter nodes