Installer hangs and eventually crashes with empty cache

If running Qt Installer with empty cache, it succeeds to download about 25% of updates.xml files, then it hangs and eventually stops with errors:
[519648] Warning: stream 167 finished with error: "Connection closed" (qtbase\src\network\access\qhttp2protocolhandler.cpp:1307, void __cdecl QHttp2ProtocolHandler::finishStreamWithError(struct Http2::Stream &,enum QNetworkReply::NetworkError,const class QString &))

If quitting the installer while it is in the middle of the 'hang' :
[23661] Fatal: ASSERT: "d->hasException" in file qtbase/src/corelib/thread/qfutureinterface.cpp, line 577 (qtbase/src/corelib/thread/qfutureinterface.cpp:577, )