5-GB thumbnails removed, but the space has not been freed! Why?

I have a Sony Z3 dual sim version (D6633) running KitKat (4.4.4). I am posting here because I understand this issue is not Z3-specific and can affect most phones. In fact, it also affects Lollipop.

The CCleaner app revealed I had > 5 GBs in thumbnail files. I used the same app to delete them. The folder DCIM\.thumbnails became empty, but the available space hasn't changed. If I go to settings -> storage, Android tells me I have 2.50GB available (same as before deleting the files) and 7.32 GB in apps. There's no way I have 7.32GB of apps! If I use the storage analyzer app (https://play.google.com/store/apps/d...analyzer&hl=en) it tells me I have 5.57GBs "used by android/inaccesible files". In other words, it seems that removing the 5GBs of thumbnails has not saved any space!

This app (https://play.google.com/store/apps/d....mydrive&hl=en) shows I have 9.07GBs occupied, but when I break it down by categories or file type, the total is nowhere near 9 GBs!


I tried all the suggestions listed at: https://code.google.com/p/android/is...Stars&id=39546
including #152 and #153:

• I got Android to recreate the files by taking videos and photos with the camera, then replacing the .thumbnails files created with small files (I created small text files and renamed them with the same name).


• I filled almost the entire remaining space with video file in the hope that the issue was caused by sparse files and Android would reclaim the space. It didn't.


• I deleted the data from the media storage app


• I wiped the dalvik cache and the cache rebooting in recovery mode

Having 5GB, out of the 11.5 available, vanish for no reason is a really unacceptable bug! Makes me wish I had an iphone :(
Has anyone found any solution?

Thanks!