Invoicing Errors for overnight services over month end

There is a serious bug with the invoicing of overnight services that run over month end.

I have just discovered that the portion of the service that fall into the later month is being invoiced at a charge of £0.00.. When I voided the invoice and checked everything and then processed the invoice again it then did add the charge, I hadn't actually changed anything..

Re-running the accounts report still shows this service as unvoiced even though it is clearly shown on the new invoice..

I would imagine that if this bug has been around for a while it has probably costs up a fair amount of money but we naturally assumed this had all been tested and was working correctly..