Hi Alexey, I managed to make a log download of 150 MByte in approx. 4 hours via the ESP8266 wifi link. This was with a PixRacer with Arduplane 4.0.3, ESP firmware 1.2.2 and the daily build QGC with the patch from @DonLakeFlyer for infinite retries. The Pixracer was powered via USB and there were no further peripherals. I could however not connect at all in the production vehicle where I have RFD868 at Telem1, a raspberry pi zero at Telem2, GPS at Serial 3, Frsky telemetry at Serial 4 and the Wifi at Serial 5. I turned out that once we disable Serial2 (the Raspberry Pi) or set the baudrate of Serial2 to 9600 Baud - then we can connect with the ESP8266.