The krpc_connect() function is returning KRPC_ERROR_DECODING_FAILED on my Arduino Uno. The request is getting through because the permission window pops up on KSP with the correct client name. The krpc_connect() function returns immediately (not waiting for me to approve on the UI) with that error. The Arduino code then retries (because the error is non-0), and the retry blocks before even sending anything (the TX light doesn't light up).

do {
  error = krpc_connect(conn, "Arduino Example");
  if (error != KRPC_OK) {
    blink_led(-(int) error);
    delay(100);
  }
} while (error != KRPC_OK);

I'm running mod version 0.4.4, Arduino library 0.4.4 (from the Arduino Library Manager), on KSP 1.3.1.1891 on Windows 10, over COM3 (USB).