Hi Xperia/Android/Mobile sifus and pros,

First off, 16GB internal storage is a pain to use on an Android 6.0 phone. 

My XA Ultra Dual (F3312) internal storage space is always filling on its own. Every time it reaches 90% I will remove apps. Despite that, it will gradually fill up to 90%+ again and I will remove apps again. The process repeats.

Here's what I've done so far :
1) Remove apps. Never reinstalled or installed new apps
2) Ocassionally cleared out apps data
2) Ocassionally clearing out the cache data
3) Ocassionally transferred media files to SD card
4) Delete FB Data, WeChat and Whatsapp chat data after backing up to cloud.
4) Clean storage of duplicate/obsolete/junk files with SD Maid Pro(Paid App) and CCleaner
5) Bought a 32GB high speed Class 10 UHS-3 (R:90/W:80) Micro SD to set up as adoptive storage to store apps.

None of the above seems to help. Some times I even removed most of the apps except FB, Whatsapp, WeChat and all but the storage just gets filled up in time until I have no more space to work with and are forced to factory reset the phone. Adoptive storage doesn't help either as most of the apps can only be installed into the internal storage.

Can anyone tell me what's taking up all the space in my phone's internal storage?.

Thanks for reading. 

But but... I delete the app data after backing up to PC using WeChat Windows app. 

Now I'm really starting to suspect WeChat...
Sigh..if Sony don't release 7.0 update with the capability to remove bloatware I'm gonna root it and remove them all..