The update to 4.0 happened to me in the middle of a track day and that was very unnerving. But so far I not been able to record a session successfully since the update. In one case, it starts but the the video goes black after a 30 seconds or so. In the other, it just never started recording.
Also, when I transfer via Wifi to Race Render, the speedometer is now very low resolution updating only every many second intervals, not continuous. This wasn't the case before.
Luckily the old version successfully recorded the first three session of that day, but I'm worried at the next track day, it's not going to work anymore.
I'm using it with Kiwi3 and no external GPS. Anyone else having luck with the Track Addict v4.0?