Periodic malfunction of SD slot.
Randomly the camera will read that the SD card is in the lock position. It's not. Is there a sensor that could be causing the problem. Sometimes leaving the camera on will correct the problem, as will removing the lens and turning it off and on repeatedly. It can go for days and be fine then stop working. I've used canned air sprayed into the SD slot, which worked once. But nothing works consistently leaving me to believe none of my "fixes" actually worked.