My wife's S4 Mini has run out of space in the device storage. We can't even install a tiny app such as Disk Usage (hoping to find where the space has gone).
So we moved a couple of large files (about 600Mb in total) from device storage to the SD card (at least 32Gb, probably 64Gb).
I have an Android HTC One SV (Android 4.1.2, HTC Sense 5.0, not rooted). It's recently been struggling for storage space to the point where it was reporting low and then critically low storage. Note this is the app storage, not anything to do with the built-in or external SD cards.
tl;dr: Is there a known issue with "dead files" cluttering up App Storage?