When a Pledge is created with the AUD currency and an installment in that pledge is written off completely in AUD, the write off happens in USD and it leaves a balance on the installment.
We are currently evaluating this issue for a fix in a future service pack.
Steps to Duplicate
1. Create a new constituent or find any constituent already in the system. 2. Add a Pledge to the constituent in AUD currency. Set the exchange rate to Spot rate and set the rate to the current AUD to USD exchange rate. Add any amount and choose any designation. Set the pledge to have multiple installments. 3. Completely write off the first installment on the Pledge in AUD. 4. Edit the pledge and click on Edit installment designations. 5. Notice the first installment is not written off completely. Adding a payment to the pledge should apply it to the next installment since the first one is written off, however, since the first installment is not completely written off, it tries to apply the payment to the remaining balance on the first installment.