Answer
The main direct risk when exchanging currency during a transit transfer is losses on exchange rate differences. Money can pass through rubles, dollars or euros, and each exchange reduces the total amount, especially if the exchange rate differs from the expected rate.
There is also a regulatory risk: the European Union regularly imposes bans on financial ties with Russia. This can affect the availability of routes, the willingness of banks to accept payments and the requirements to explain the origin of funds.
Before making a transfer, you need to consider not only the fee but the full route the money takes: where the exchange occurs, at what rate, who the sender is, which country is involved, and which documents will remain after the transaction. Otherwise, a technically successful transfer can be expensive or difficult to explain.