It turned out to be some hardware issues. I had ~10 email correspondence with the Viofo CS; they are terrible. They asked me to flash the firmware in multiple ways, then to open the case to reconnect the cable. None of them worked. Eventually, they wanted me to ship the unit to China for repair. I have to pay the shipping myself for this under warranty item!
I give up on it. The shipping cost will probably buy me an Aukey, Anker or some other Amazon brands. Some people mentioned about soldering a capacitor or whatnot, I'll check if it's worth a small DIY time. Otherwise, I'll give it to someone who knows these stuff for free.
The Viofo took better video than some other brands I have/had (Mivue/Garmin). But when it failed, I didn't get any warning/beeping. I'm glad I found it after a week or so. And obviously, the Viofo CS inherited the third-world mentality just as many other Chinese manufacturers.