Autoinvoice reject transfer amount of the credit can't exceed the balance of the item its crediting.

have a credit memo that is being rejected on autoinvoice. two reasons;-

1 The total amount of the credit memo can't exceed the balance of the debit item it's crediting.
2 The tax line of the credit memo doesn't have a link to the invoice.

The invoice amount is the same as the credit memo, there are no receipts or credits against the invoice - so balance still open. Error around exceeding does not make much sense

Any suggestions?

Rgds

Stephen