Freight Adjustment creates duplicate entries in GL

We use Freight Match functionality - a standard functionality available in P4314 to create vouchers from Freight History.  When the Invoice amount does not match with the freight amount in freight history users do a freight adjustment using a row exit.  The adjustment transaction adds records to freight history table (F4981) and also creates transactions in GL with a 'G' batch.  In most cases this functionality works flawlessly without any issues.  On rare occasions though, it adds records correctly in the freight history table but adds two sets of records in the GL.  The two sets are created with the same document type and number, same amount but have a different batch