Using  the camera Upside down, and correctly shown on the camera, the thumbnail is wrong.  

Hello, there. Sorry for the inconvenience. May we know if your video is upside down as the way you shot it?
Please make sure the "Orientation Lock" is turned on.

Hi Fishycomics. Thanks for the detailed test video.

We repeat the test u made and view it in PC, smart phone , the TV in our office. We cannot reproduce it.
Based on my experience, the issue is with the specific device to view the media.

There are standard criteria for a thumbnail for a video and action3, PC , smartphone follows it.
That's why when using these devices to view  the footage, it is correct.

The possible reason maybe:
1.the TV might not correctly interpret the orientation of thumbnail.
2.some devices like to grab the stream as the thumbnail without interpret the footage orientation.

When only one person represents the issue,  lets see if others will join in,Issue exists not just with me on the thumbnail upside down, the OSmo Action plays perfect, and so does the competitor GoPro