My phone Iocean X7S has opportunity to save apps to either internal storage, phone storage or external SD-card. However, I can't use phone storage as apps saving location. There is Phone storage and SD card opportunities in Settings -> Storage -> 'Default write disk' . However, whichever I choose as primary, there doesn't happen anything. If external SD card is mounted, there is "Move to SD card" button in apps and a tab 'SD card' in Settings -> Apps. If I unmount SD card, there disappears opportunity to choose primary save location, SD card tab and button to move app another location. However, there reads 'Phone storage app 0.00B' and 'Phone storage data 0.00B' in apps instead of 'SD card app and data' when SD card is unmounted. So I think it is some kind of software issue.
I have tried factory reset different ways without any result, there is still only opportunity to keep apps in internal storage or SD-card. In \storage\sdcard0 is external SD-card and \storage\sdcard1 is phone storage.