I am not educated on Android enough to figure this out on my own. My problem began New Year's Eve with error messages saying device memory was full. My Galaxy S2 Skyrocket began to lag and wouldn't allow me to access photos or contacts. It would freeze. I'd remove the battery when it would get stuck restarting. I looked in "Storage" and found that the device's memory is only 1.97gb. Then I noticed that there was 11.26gb going to USB storage. Where did my memory go? I was told by a tech friend that I may have a "hidden partition." I appreciated a very basic, non-technical explanation on how to fix this. Thanks.
I had a similar issue where I could not figure out what was taking up my phone's storage. I used an app called DiskUsage to visualise the issue and find the folder causing the problem.
When I was developing two years ago I altered the GPS settings on the device and they started outputting .txt files to the SD card. This made no sense to me and after looking into it if an application installed has this issue it will persist until the application is removed. I can not remember the folder location.
I want to say /sdcard/gps/* but here is a reference if this was the issue: SD Card fills up with GPS/*.txt files