I have nothing set to record in sentinel and i checked in the scanner menu and it showed nothing recorded.
Then i had trouble reading the disk so i had to do the whole routine CUD reprogram the whole nine yards. Weird as i have not gone near this scanner for a few weeks now. It's been on and scanning the whole time. Today when i went to update a few things is when it got all upset.
If it is still acting up, you could try connecting the scanner to your computer via the USB cable in Mass Storage mode.
Then open your Windows Explorer and you'll see the scanner showing up as a removable drive. You can right mouse click on that drive, then go down to properties and see how much used and free space there is. That'll tell you how full/empty the SD card is.
Following that you can, using Windows Explorer, navigate through the various file folders on the SD card and see if anything jumps out at you as far as being unreasonably large. There are two sub folders in the audio folder (inner_rec and user_rec). You may see some WAV files in them. There may also be some files in the Discovery folder if you've done any Discovery sessions.