AP /GL 8.9 : Journal generator with Edit creating AP journals based on current rate instead of user

Under what scenarios.. journal generator with edit or online journal edit creates or calculates AP journal amounts with the current exchange rate and not the exchage rate specified on the voucher.

We create vouchers with a user defined exchange rate for USD to INR. Our base currency is INR. the user defined exchange rate we specified is 56.58. When we post teh voucher, this rate is used.

But something not always when we journal generate the voucher with edit checked, the exchange rate in GL is calculated as the current exchange rate and not the rate specified on the voucher.

I am not able to duplicate this at my own level. But this happens sometimes on adhoc basis. We need to know why this discrepancy happens and what can we do to avoid it. Please advice. This is urgent as it affects our closing issues.