diff --git a/.github/workflows/_base-server-tests.yml b/.github/workflows/_base-server-tests.yml
index f269e0bde6..81e90599dc 100644
--- a/.github/workflows/_base-server-tests.yml
+++ b/.github/workflows/_base-server-tests.yml
@@ -55,7 +55,6 @@ jobs:
     timeout-minutes: 30
     env:
       NODE_ENV: "production"
-      PYTHONOPTIMIZE: 2
       # noisy 3rd party library warnings
       PYTHONWARNINGS: "module,ignore:::babel.messages.extract"
       DB_ROOT_PASSWORD: db_root
diff --git a/.github/workflows/_base-ui-tests.yml b/.github/workflows/_base-ui-tests.yml
index 7617a6abd6..cc9b09bf1f 100644
--- a/.github/workflows/_base-ui-tests.yml
+++ b/.github/workflows/_base-ui-tests.yml
@@ -44,7 +44,6 @@ jobs:
     timeout-minutes: 30
     env:
       NODE_ENV: "production"
-      PYTHONOPTIMIZE: 2
       # noisy 3rd party library warnings
       PYTHONWARNINGS: "ignore"
       DB_ROOT_PASSWORD: db_root
@@ -92,7 +91,7 @@ jobs:
             -x '${{ github.event.repository.name }}/public/dist/**' \
             -x '${{ github.event.repository.name }}/public/js/lib/**' \
             -x '**/*.bundle.js' --compact=false --in-place ${{ github.event.repository.name }}
-      
+
       - name: Site Setup
         run: |
           source ${GITHUB_WORKSPACE}/env/bin/activate
@@ -102,7 +101,7 @@ jobs:
       - uses: browser-actions/setup-chrome@latest
       - run: |
           echo "BROWSER_PATH=$(which chrome)" >> $GITHUB_ENV
-    
+
       - name: Run Tests
         run: |
           source ${GITHUB_WORKSPACE}/env/bin/activate
diff --git a/frappe/core/doctype/rq_job/test_rq_job.py b/frappe/core/doctype/rq_job/test_rq_job.py
index d9090c0853..f688a92248 100644
--- a/frappe/core/doctype/rq_job/test_rq_job.py
+++ b/frappe/core/doctype/rq_job/test_rq_job.py
@@ -175,7 +175,7 @@ class TestRQJob(IntegrationTestCase):
 		# If this starts failing analyze memory usage using memray or some equivalent tool to find
 		# offending imports/function calls.
 		# Refer this PR: https://github.com/frappe/frappe/pull/21467
-		LAST_MEASURED_USAGE = 42
+		LAST_MEASURED_USAGE = 46
 		if frappe.conf.use_mysqlclient:
 			# TEMP: Add extra allowance for running two connectors, this should be rolled back before v16
 			LAST_MEASURED_USAGE += 2
diff --git a/frappe/model/base_document.py b/frappe/model/base_document.py
index b79724f53a..8a584d33aa 100644
--- a/frappe/model/base_document.py
+++ b/frappe/model/base_document.py
@@ -22,6 +22,7 @@ from frappe.model.dynamic_links import invalidate_distinct_link_doctypes
 from frappe.model.naming import set_new_name
 from frappe.model.utils.link_count import notify_link_count
 from frappe.modules import load_doctype_module
+from frappe.types.docref import DocRef
 from frappe.utils import (
 	cached_property,
 	cast_fieldtype,
@@ -864,6 +865,10 @@ class BaseDocument:
 			if not docname:
 				continue
 
+			assert isinstance(docname, str | int | DocRef) or (
+				isinstance(docname, list | tuple | set) and len(docname) == 1
+			), f"Unexpected value for field {df.fieldname}: {docname}"
+
 			if df.fieldtype == "Link":
 				doctype = df.options
 				if not doctype:
diff --git a/frappe/tests/test_document.py b/frappe/tests/test_document.py
index b970f8068a..a00da96df7 100644
--- a/frappe/tests/test_document.py
+++ b/frappe/tests/test_document.py
@@ -207,6 +207,9 @@ class TestDocument(IntegrationTestCase):
 
 		self.assertEqual(frappe.db.get_value("User", d.name), d.name)
 
+		d.append("roles", {"role": ("Guest", "Administrator")})
+		self.assertRaises(AssertionError, d._validate_links)
+
 	def test_validate(self):
 		d = self.test_insert()
 		d.starts_on = "2014-01-01"