Steps to fix without losing progress:
1. Go to Internal Storage / Android / Data
2. Copy zombie folder to another location outside of android folder, at least 2 location (to be sure you wont lose progress)
3. Uninstall the app
4. Install the app
5. Copy the backed up zombie folder to Internal Storage / Android / Data
6. Play and enjoy
Doing this since early stages of the game development, works 99% of the time. Keep in mind to make sure you use the same apk file / provider, to avoid build issues.