fix: override _seek_for_lines to correctly identify counterpart lines based on destination_account_id

models/account_payment.py

@@ -124,4 +124,45 @@ class AccountPayment(models.Model):
                 payment.realization_id.expense_sheet_id.invalidate_recordset(['state'])
         return res
 
-
+    def _seek_for_lines(self):
+        """
+        Override _seek_for_lines to explicitly force the destination_account_id 
+        to be recognized as the counterpart_line.
+        
+        Native Odoo sometimes misclassifies the advance/expense account (e.g. 118101) 
+        as a write-off line if it's not strictly a receivable/payable account type. 
+        Simultaneously, if a tax deduction account (e.g. 217103 PPh 23) is a payable account type, 
+        Odoo erroneously classifies the deduction as the counterpart.
+        This causes duplicate lines when regenerating the journal entries.
+        """
+        self.ensure_one()
+        
+        # Capture the original output
+        liquidity_lines, counterpart_lines, writeoff_lines = super()._seek_for_lines()
+        
+        # If there's only one line in write-off, Odoo native might have forcefully moved it 
+        # to counterpart. But we need to make sure the correct counterpart is identified based 
+        # on the configured destination account.
+        
+        if self.destination_account_id:
+            # We want to re-evaluate counterpart vs writeoff based purely on destination_account_id
+            
+            # Reset counterpart and writeoff
+            all_non_liquidity = counterpart_lines + writeoff_lines
+            new_counterpart = self.env['account.move.line']
+            new_writeoff = self.env['account.move.line']
+            
+            for line in all_non_liquidity:
+                # The primary destination account is the counterpart
+                if line.account_id == self.destination_account_id:
+                    new_counterpart += line
+                else:
+                    new_writeoff += line
+            
+            # In edge cases where Odoo couldn't find ANY counterpart, let's preserve Odoo's fallback 
+            # if our logic resulted in empty counterpart but native didn't. 
+            # However, typically the destination_account_id *must* be the counterpart.
+            if new_counterpart:
+                return liquidity_lines, new_counterpart, new_writeoff
+                
+        return liquidity_lines, counterpart_lines, writeoff_lines