Interesting info. In my country a local representation of DOD company claims there is a buffered-record, so i bought RC500S for testing purposes. On my first try, it looked like it doesn't work so i've contacted a support and they told me that there truly is this function and it works (they claim there is a newer version of this dashcam). They suggested me to use Kingston/Samsung UHS-I U1 card (i was using 128GB U3 Samsung card) so i bought Kingston 16GB U1 and now it works. So far so good i just hope it's not due the lower capacity of the card (i will try in a near future).
At this moment IQ is pretty good, camera works, only mobile app has some bugs. The only thing which drive me crazy is awfully slow Wifi. Seriously man, live stream of recorded footage is not possible to view due buffering and when i tried to download it to my phone it takes minutes to download 450MB(3 minutes) video.
EDIT: Ok, another issue, when i park in garage (no light whatsoever) it records continuously because of video noise (which "moves").