[Android Q&A, Help & Troubleshooting] Xupicor:
I own a Nokia 6, never rooted, 8.1.0 with the latest security patch installed (1 August 2018).

I have 32 GB internal shared storage and 64 GB microSD card installed. Be it a good or bad idea, I have formatted the card as internal storage, and migrated data to it using options available in Android settings, no third party shenanigans.

When I look at apps' details, those that have the option to choose storage signify that they are on sdcard.

Now, to the problem: I approached about half of used space on the sdcard, that's a bit over 32 GB, and I'm closing in on about half on the internal shared storage, that's about 13.4 GB used at the moment.

However, even though it would look like I have lots of unused space left, the phone started to act as if I don't have any. But... Not always. Let me elaborate.

I can't make a picture or record video, all I get is: "there was a problem with saving your photo or video."

I can't download files using a browser. It instantly fails.

I can't install apps from Google Play Store like "Google" and many others, however, I can install some other apps, seemingly at random (but if it fails, of keeps failing).

I can - because I just did - download security patches from settings/system updates....

From the above I speculate without any specific Android knowledge that:

- the internal shared storage isn't a single partition spanning the whole of built-in memory but rather is partitioned into multiple... Well, parts, therefore:

- there's probably a /system, /data and /user partition (forgive the layman guesswork on the names). There's probably also a /swap like in *nix? Then again, I guess not because that would probably slowly kill internal storage flash memory...

Anyway, from the above I gather that the simplistic reporting on how much internal storage I used doesn't let me know that I might have ran out of space on one of those discrete partitions.

That might explain why some apps I can install (they can be installed in external storage, so they do) and some I can't (they need to be on internal storage for whatever reason).

I have tried looking at the app info to maybe move apps to SD card but any and all I check either don't have the option or they already are on SD.

I tried deleting files and removing apps with various results:

- some files I just can't remove, even though they don't appear to be in use (still, maybe they have handles open, I don't know how to check for that apart of forcing suspected apps close)

- some apps (HERE Maps) left a considerable amount of junk in Android/data after themselves, and none of my file managers seem to be able to delete these files.

- some files and apps deleted just fine and the used space indicator did reflect that, however...

I still can't save a photo or video, or download a file, and apps still either install or not, just like before.

That got me thinking that there may be a problem with file/directory permissions for some bizarre reason.

I'm stumped. I'm on the go, visiting Milan tomorrow and I won't be able to take a single photo. Not that Nokia 6 has a great camera, but it's there and I can't use it when I need it.

Halp?