It would be best to wait for
@h-elsner to comment before doing anything drastic.
My limited knowledge of this problem would be to suspect a bad battery or corrupted firmware.
Do you have a way to check the actual battery voltage with a multimeter?
If it is bad firmware, There are about three levels of recovery you can try:
1.) Factory Reset. This is done from the settings screen. I'm not even sure you can go to that screen in your current situation.
2.) Reloading the firmware via the normal update process. (See Below)
3.) There is also a thread for doing a much more complex recovery of the system that might apply. See
ST10/ST10+ TWRP Install Guide | Yuneec Drone Forum (yuneecpilots.com)
But if the problem is NOT corrupted firmware, any of these attempts may make things worse than they are.
Hence the recommendation to wait on @h-elsner before doing anything more than check the battery voltage. He's in Germany. It's about 2 AM his local time right now.
(From Above): The official Yuneec ST10+ update instructions are easy to misread and have led to problems for several folks.
If and when update seems warranted, I would recommend using the instructions of Attachment 36 (ST10+ Firmware Update) of the PDF document attached to
Way To Fix Drones project. Note the file download links at Step 2 of that document are currently
not working due to problems with the Yuneec Websites. You can get the needed file from:
ST10+ Controller - Dropbox