The problem I'm having regards a cheap Chinese phone which is rebranded and sold in my country as Manta MSP94501 Easy Selfie. It runs Android 5.1 (with a KingRoot which I installed) and lately, it started very aggressively reporting lack of free storage - the widgets don't want to start, I get constant alerts that this or that couldn't be updated because of insufficient storage, that Google Play Services won't work until they're updated (and yet they don't want to be updated cause - again - insufficient storage), I can't install any new app either and the phone started getting a bit sluggish on top of all that.
The problem is, this phone has 8GB internal storage (half of which is allegedly the one for the phone and not the system) and is virtually empty (a few photos and videos, literally not more than a few apps). When you go into Settings->Storage, it reports that there's 4.51GB total for the phone storage, with 252MB free and yet the specific list below doesn't reflect that at all, as it reads: 3MB for Apps, 601MB for Photos and Videos, 40KB for Sounds, 348KB for Downloads, 24MB for Cache and 8.3MB for Other. As you can see, this does not sum up to 4.3GB at all - and the coloured bar above the list shows the storage correctly (that is, 3/4ths of it is marked grey as empty space - which is the truth!) but still, all the readings show otherwise, alerting about the 252 free megabytes.
What can I do? I've tried clearing the cache from recovery, clearing Google Play cache - but all to no avail. Here are also the pictures of what I described above (in Polish but those are pretty self-evident I think and I also translated above): https://imgur.com/a/YfTTJ
Any suggestions? :(