GoPro Manual File Recovery I’ve never actually used any of the labs firmware but I found this tidbit interesting for repairing an improperly closed file. Reproduced here for posterity:

# Useful Tip - Manual File Recovery

So you have a corrupted/unclosed GoPro file. You crashed your drone, and the battery was disconnected before the file was closed, or you ran your car wheel over a recording GoPro, crushing it. If your SD Card survived, the file is likely recoverable using another GoPro.

0. You need any working GoPro camera, although the same model and firmware version is advised. If you’re using Labs Firmware and are using Altered file naming (this page’s Labs feature), reset the filenaming to the default.
1. Copy the file you want to repair to your PC
2. With a working GoPro, record for 10+ seconds then pull the power or battery, while still recording. You want an intentionally unclosed file. The camera will remember it needs to repair only this file
3. Add that SD Card to your PC directly (not via camera USB)
4. Copy the filename of the last MP4 captured. e.g. “GX010358.MP4”
5. Delete this dummy file from the SD Card
6. Add your previous corrupted (unclosed) file to the SD card, and rename it to the copied name. e.g. If your filename was “Drone03_GX010201.MP4”, or just “GH010330.MP4”, rename it to “GX010358.MP4” (your last MP4 filename)
7. Insert the SD Card with your corrupted file back into the working GoPro camera
8. Power on the camera, and the “last” file will be repaired
9. Once the camera completes the file repair process, you can eject the SD Card and backup and play the now repaired file

Compatibility: Labs enabled HERO8, HERO9, HERO10, HERO11, HERO12, HERO13, MAX and BONES