R12.1.3 strange amounts in balance due window of an applied Credit memo

Hi,

we have the following strange behaviour when doing the following:

1. we book a transaction with vat code of 22%, line amount 300, tax amount 66.
2. We adjust the tax amount on the invoice with an activity of type Tax for -66.
3. Our invoice is now open for 300.
4. We book a credit note for the same customer, with the same vat code, line amount -300, tax amount -66.
5. We adjust the tax amount on the CM with an activity of type Tax for 66.
6. Our CM is now open for -300.
7. We apply the CM to the invoice for the total amount of 300 in order to close the balance due of both transactions.