I realize that’s speculation, and I think it’s an interesting idea. One of my observations with this problem on Cam Pan v3 (apologies to @alan69700 for the diversion from battery-cam-pro) has always been that the Cam where I’ve had consistent issues with microSD card recognition, recording, and playback is the device with the more recent Activation Date. After reading your comment, I do wonder if Cam Pan v3 firmware released after a certain date writes something weird to an inserted microSD card that becomes problematic. The microSD card in my older Cam Pan v3 has been there since I set it up, and I’ve never had a compelling reason to reformat it. Now your comment makes me wonder if trying an in-Cam reformat (or doing something like ejecting and re-inserting the card) would hose that one, but I’m not curious enough to risk it. 