Boomerang Transactions could be the result of posting twice to the same account
From NewViews help
“the single resulting journal row, posting twice to the same account, is treated as a boomerang. The only difference for a boomerang is that the resulting postings do not appear on account debit/credit views or contribute to account debit/credit histories. The only material consequence of this is that the import reported bogus history amount errors when checking the imported account histories. The importer now detects and compensates for these rare transactions.”
If you switch from balance forward to open item, a boomerang transaction is suggested as in the New Views help item following
“To switch from open item to balance forward, print the open ledger view as the final open item statement. Continue by using the balance forward method. To switch from balance forward to open item, print the final balance forward statement, close all items, and add a boomerang transaction with an amount equal to the balance of the account. The boomerang transaction creates two items on the same account, one with a positive amount, and one with a negative amount. Close the negative item. The open ledger view then contains one item with an amount equal to the total due. Continue by using the open item method.”
There are other instances of “boomerang transactions”. If you type “boomerang transactions” in Newviews help, you can display them to see if they apply.