diff --git a/scripts/addons_core/bl_pkg/bl_extension_ui.py b/scripts/addons_core/bl_pkg/bl_extension_ui.py
index bf62218652f..0c65ac97af7 100644
--- a/scripts/addons_core/bl_pkg/bl_extension_ui.py
+++ b/scripts/addons_core/bl_pkg/bl_extension_ui.py
@@ -561,6 +561,30 @@ def addons_panel_draw_items(
     return module_names
 
 
+def addons_panel_draw_error_duplicates(layout, error_duplicates):
+    import addon_utils
+    box = layout.box()
+    row = box.row()
+    row.label(text="Multiple add-ons with the same name found!")
+    row.label(icon='ERROR')
+    box.label(text="Delete one of each pair to resolve:")
+    for (addon_name, addon_file, addon_path) in addon_utils.error_duplicates:
+        box.separator()
+        sub_col = box.column(align=True)
+        sub_col.label(text=addon_name + ":")
+        sub_col.label(text="    " + addon_file)
+        sub_col.label(text="    " + addon_path)
+
+
+def addons_panel_draw_error_generic(layout, lines):
+    box = layout.box()
+    sub = box.row()
+    sub.label(text=lines[0])
+    sub.label(icon='ERROR')
+    for l in lines[1:]:
+        box.label(text=l)
+
+
 def addons_panel_draw_impl(
         self,
         context,  # `bpy.types.Context`
@@ -580,14 +604,26 @@ def addons_panel_draw_impl(
 
     from . import repo_cache_store_ensure
 
+    layout = self.layout
+
+    # First show any errors, this should be an exceptional situation that should be resolved,
+    # otherwise add-ons may not behave correctly.
+    if addon_utils.error_duplicates:
+        addons_panel_draw_error_duplicates(layout, addon_utils.error_duplicates)
+    if addon_utils.error_encoding:
+        addons_panel_draw_error_generic(
+            layout, (
+                "One or more add-ons do not have UTF-8 encoding",
+                "(see console for details)",
+            ),
+        )
+
     repo_cache_store = repo_cache_store_ensure()
 
     # This isn't elegant, but the preferences aren't available on registration.
     if not repo_cache_store.is_init():
         repo_cache_store_refresh_from_prefs(repo_cache_store)
 
-    layout = self.layout
-
     prefs = context.preferences
 
     # Define a top-most column to place warnings (if-any).
diff --git a/scripts/startup/bl_ui/space_userpref.py b/scripts/startup/bl_ui/space_userpref.py
index 4e98dd8018b..5ecbed74778 100644
--- a/scripts/startup/bl_ui/space_userpref.py
+++ b/scripts/startup/bl_ui/space_userpref.py
@@ -2617,7 +2617,6 @@ class USERPREF_PT_addons(AddOnPanel, Panel):
         if filter in {"All", "Enabled"}:
             # Append missing scripts
             # First collect scripts that are used but have no script file.
-            module_names = {mod.__name__ for mod in addon_modules}
             missing_modules = {
                 addon_module_name for addon_module_name in used_addon_module_name_map
                 if addon_module_name not in module_names