I use a Samsung High Endurance 128 GB card, formatted about once a month, just whenever I want to pull the card to view videos. Recently I've been formatting it about once a week as I try to troubleshoot this latest powering-off issue.
This is the exact same type SD card I use in my other dashcam, a Viofo A129, and have done for nearly a year without issue in that device. I treat it about the same way - pull the card to verify proper recording, and format before putting it back in the dashcam - once a month or so.
Yes, I checked both after purchase to verify their performance. They came in genuine packaging, and passed h2testw testing. No reason to think either is counterfeit.
I do have an older, 16 GB Sandisk Ultra card (U1 speed) that I use for loading firmware updates on both dashcams. Tell you what, I'll format it and use it for recording for the next week or so, just to see if the K2 behaves differently.
Meanwhile, here's some more data from yesterday's riding, with the usual 128 GB Samsung SD card:
One trip was less than 5 minutes. K2 started up and recorded normally the entire time. K2's WiFi was connected to my phone as usual.
About 2 hours later, I took a longer ride. This is where it gets weird. FWIW, I use 3-minute clips.
The K2 powered up and began recording at 18:04:42. From the video it looks like this is when I turned the bike's key on, in my friend's garage. But it only recorded for 1 minute 24 seconds. This clip has a "wrench" flag in Dashcam Viewer, which says "Bad GPS time value detected in at least one point. Applying a fix."
Meanwhile the K2 was connected to my phone's WiFi, so I assumed was recording normally. Nope. It didn't record the following 30 minutes or so.
The next video clip is timestamped 18:42:22, is abnormally small (36 MB) and is unplayable.
The one after that is timestamped 18:55:42, and is normal, with correct timestamp and filesize. Plays fine.
Same story for the next clip (18:58:43).
Though I was out riding for the entire period from around 18:00 to 19:30, there are only 2 more clips after that.
One is timestamped 19:01:43 and is almost the size of a full 3-minute clip (~300 MB), but is unplayable.
The next one is stamped 19:04:27. Small file (~20 MB), unplayable.
Nothing after that.
While I was out, I noticed that the K2's WiFi was no longer connected, some time around probably 18:30. I stopped and looked - the K2 was powered off. No activity LEDs, no WiFi connection. Tried to turn it back on - same thing as I've seen previously, where it would start to power up but wouldn't stay on. Gave up, rode home. Pulled over after I got off the highway, again manually turned the K2 back on (using the silver button). That was around 19:00. It is now clear that though the K2 looked like it was working normally after that, and until I parked at home, it was either recording corrupted files or not recording at all.
So there are actually 2 things going on here:
--The K2 can be connected to WiFi, and appear to be working normally, but either not recording at all, or recording unplayable, corrupted video files.
--The K2 will also shut itself off and then refuse to stay on when manually turned back on, seemingly at random. I thought it may have had something to do with heat the last 2 times, but now I'm not so sure.
WTF.
I did order a new Sandisk High Endurance 256 GB SD card. I had been planning a storage upgrade anyway. Meanwhile I suppose I'll run the existing, 128 GB Samsung card through some tests.
BTW, the picture below shows where the K2 DVR is installed on my Vstrom. You are looking at the inside of the right side fairing, from the left side of the forks, K2 DVR is at upper left. It is stuck to the plastic with some Velcro. There is a big vent at the front of the fairing (to left of picture) so the DVR should receive plenty of airflow when moving at any speed. I can't imagine how it could be overheating here, if it is designed to work when under a seat (where it would get much much less air).