Hello, I am having problems with a Pix32v5 running ArduPlane V4.2. I was fly south about 1400 feet away in auto tune, when I lost RC signal. I went after it and regained signal again as I was bringing it back to land I kept losing RC signal intermittently. I switched it into Manual flight mode, and regained signal. Then I switched back to Autotune, and retained RC signal while landing.
https://drive.google.com/file/d/1oGEKWQa5ZbD5RR35JxxwEj2BYeMYbPDi/view?usp=sharing
Do some more ground testing of your RC link, what rx are you using?