It's definately soft error. I don't know why it is happening but I solved it then reinstalling soft. I think you upgraded your OS and then this started to happen. I spotted that OS sometimes writes with error - I men everything is OK when U upgrade but it comes with some kind of bugs like this error. My app world dissapeared several times and after 5th time of writting OS everything went good and no I have no error. Once again - I don't know but I see only one solution - wipe your device and write new OS, it can take several times to write it. To me it took 5 times of writting and then everything was good.
Sorry for my english but I hope you understood what I mean GL