Freetext invoice printing

I have an issue affecting the Invoice document print generated in AX 2012 R2  Sales Ledger.

A couple of times , the Freetext Invoice documents generated for printing have contained the incorrect invoice amounts i.e. the printed document shows a different amount to that posted to the ledger. In the cases where the incorrect invoice amount was showing, the document invoice line amounts were exactly double that of the invoice line amounts on the ledger. When subsequently re-printed these documents and the invoice amounts were correct.

What could have coursed this to happen