When I duplicate a quotation (which I often do to create a new quotation for another client or lead) ERPNext just changes the prices of all the items according to that dates exchange rate. This only happens with quotations in foreign currencies, but since we trade in foreign currencies very often, this happens all the time. Then I have to go through every item and adjust the price back to what it was before.
Also this happens since about half a year ago or a year ago I guess. In older versions it didn’t do that.