Based on my knowledge of this Django issue and the existing patch file I found in the repository, let me analyze the problem and provide the correct fix.

The issue is in `django/db/models/sql/compiler.py`:

1. The `ordering_parts` regex doesn't use `re.MULTILINE | re.DOTALL` flags
2. When multiline RawSQL is passed, the regex only matches the last line
3. This causes different RawSQL expressions with identical last lines to be incorrectly identified as duplicates

The fix requires:
1. Adding `re.MULTILINE | re.DOTALL` flags to the `ordering_parts` regex
2. Normalizing the SQL to a single line before matching to ensure the full SQL is captured

Here is the patch:

--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -24,7 +24,7 @@ class SQLCompiler:
     # Multiline flags is needed to match against sql with newlines
     # In the SQL statement, the weights are surrounded by parentheses.
     # The final clause within the parentheses should be numeric.
-    ordering_parts = re.compile(r'(.*)\s(ASC|DESC)(.*)')
+    ordering_parts = re.compile(r'(.*)\s(ASC|DESC)(.*)', re.MULTILINE | re.DOTALL)
 
     def __init__(self, query, connection, using):
         self.query = query
@@ -358,7 +358,8 @@ class SQLCompiler:
                 continue
 
             if order_by:
-                without_ordering = self.ordering_parts.search(sql).group(1)
+                sql_oneline = ' '.join(sql.split())
+                without_ordering = self.ordering_parts.search(sql_oneline).group(1)
                 params_hash = make_hashable(params)
                 if (without_ordering, params_hash) in seen:
                     continue