QNetworkReply::finished or QNetworkReply::error not called for second request to unreachable host

I have a program that makes a sequence of GET-requests to the server. In case of the server is unreachable the first QNetworkReply finished immediately, for other replies QNetworkReply::finished or QNetworkReply::error not called.

Source code of simple program, that reproduced this error, are attached.

Program output for normal connection:

r1 started
r1 finished
r2 started
r2 finished
quit app

Program output after `ip route add blackhole $SERVER_IP` was executed:

r1 started
r1 error "Network unreachable"
r1 finished
r2 started

May be the error is related with QTBUG-57390.