@uliwooly Finally I found the solution: 😎 Data of Sony gallery apps like album,etc and a android app "Media Storage" cause this confliction. And also some app data in "android" folder is added. I clear all of that data and uninstall update the gallery apps, then update. After all and before updating restart and enjoy!! 😊
I also have this problem in my new phone; Sony Xperia Z3 Dual, and the solution is the same.😊😉😎
@Raknarod If u can see ur media files with file manager do these steps: 1.Backup ur media apps(apk files) via "app backup and restore " A. Media apps like: Picasa, playerpro, mx player and any app that play or show photo, music, movie. B. First clear all data of those apps (go to settings\apps) then uninstall them. Go to C and D steps if needed: C. Delete it's appropriate folders of those apps in root of internal or SD card memory. D. Go to this folder in internal and external memory: Android\ Data and then: Delete it's appropriate folders of those apps in this folder. Note that folders of "Android\Data" often start with "com." string like "com.picsart.studio".
2. According to ur Sony gallery apps on ur device: Gallery or Album / Walkman or Music / Video or Movie A. Clear data of those three apps I said. B. Uninstall updates of those three apps I said.
3. Go to settings /apps. In "All" tab, find App named: Media Storage ". And then Clear it's data.(Tap on Clear Data)
4. Close all recent apps by slide left or right their windows.
5. Turn off, then turn on the device.(don't restart)
Check ur gallery or Music! Ur media files of internal memory is back. 😎
6. Update ur Sony apps with Google play and restore ur backed up apk files.