For my LK-7900, the in-cam format is actually just a delete function, a quick format. So if the SD card file-system is corrupted or scrambled, it doesn't fix anything and strange stuff still happens.
This might be what you are experiencing with your LK-7950.
To fix it, I put the SD card in my PC, check if the card is OK out of curiosity (right click, Properties->Tools tab->Error-Checking, check now button) to see if the file-system is OK.
Copy config.bin to a safe place and manually format the SD card (64K, FAT32 (for 7900)- not Quick Format), takes a long time 15minutes/64GB.
Then copy the config.bin file back over, and it's all good. The cam creates the usual folders.
Sometimes I still get really old files appearing, I've erased/formatted the card and looking at it can see stuff from a couple months ago, which is strange. I usually in-cam format every time I fill up with gasoline.
Also make sure you have the latest firmware in the cam, Lukas did fix SDcard firmware-related issues years ago.
Beyond this, the SD card might be worn out.