I had a Sony Xperia C with a 16GB memory card. My internal storage kept filling up which made it unable to update or download any apps. The only apps I had were WhatsApp and Instagram. Sent my phone in. Had to pay for repairs, was in for 6 weeks, and got the phone back but still the same errors.
I got a new phone Huawei G6, a brand new 16GB, and a new Google Play Store account. The phone is set for the default storage location to SD card. Moved all app that I could to an SD card. I only have 10 songs and about 100 pictures. I clear cache every day, probably 500 every day. I really don't know what I'm doing wrong.