Before I purchased my Quanum Nova (PnF with no stock white radio) ... I saw this pilot's videos and forum posts. It clearly shows the radio making random mode changes on it's own. In the forums, he posted the corresponding log files showing the same.
This, along with similar reports from other Nova pilots persuaded me to let HK keep their $25 TX/RX radio set and I would put that money toward a better radio from the beginning. Other forum posters have also reported a high incidence of radio glitches (most resulting in crashes or fly-aways) ... some even backed-up with log data.
We are not talking GPS glitches here, but actual RC Control glitches, limited range, and randomly sent (or mis-interpreted by RX) Mode commands. There is also this issue with the power-button that several pilots have reported, and other general build issues (like flakey stick-gimbal potentiometers). One pilot even had a bad TX antennae coax-wire to circuit-board solder-joint (poor range).
I'm used to building and flying ARF planes, so installing my own radio in an aircraft is no big deal. Actually, it's more normal for me and even preferred (because I get to use what I want).
I guess the main benefits of a FrSky Taranis X9D & X8R receiver is the excellent ACCST 2.4ghz protocol, telemetry features, and ability to do real-time RSSI.