Android HTC One SV App storage full of unknown data

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? Is there any way to clear said storage out, or at least view the app storage and see what's taking up the space?** ---------- Steps I took as space became more and more scarce: - Moved apps that don't care about being on the App Storage to the SD Card - Cleared all the caches I could find - Cleared all the data I could find - Deleted all text messages - Moved apps that really don't like being on the SD Card to the SD card - Uninstalled all uninstallable apps except the ones I was actually using on a daily basis - Uninstalled updates to the non-uninstallable apps - Uninstalled apps that were actually on the SD Card out of sheer desperation Whatever space was regained by this was in the 10-50 megabyte range in total and was "mysteriously eaten" over about 2 weeks of normal usage (e.g. web-surfing on Chrome, checking e-mails). By the time I'd got to the bottom step, the automated storage tool was informing me that there was nothing to uninstall/move. When the phone finally started reporting "less than 0Mb" and crashing the basic phone functionality, I took extreme measures and "Power+Vol'Down'd" it, selecting "Clear Storage" from the BootLoader. That got me back almost 1Gb of space, at which point I was finally able to install Android 4.2.2 (up to this point, it couldn't even *download* the necessary update). I also updated all the built-in applications to current. I then installed my core application suite: - Note Everything - BeyondPod Pro - NoteEverything Pro - Amazon MP3 - Audible My phone currently reports that it has 355MB of "App Storage" available; out of 3.85 Gb. Of the used, 673MB is Apps, and a staggering *2.85 Gb* is the mysterious "Other". I want that **Other** back. The space reclamation tool merely suggests I uninstall the 5 apps above for a grand total of 66.7 Mb, which is... irritating. Is there a known issue with "dead files" cluttering up App Storage? Is there any way to clear said storage out, or at least view the app storage and see what's taking up the space?