this has has so far happened to me once... that is until just 5 minutes ago. The app went finnicky for a different reason so i had to restart the app, when i loaded a save file i accidentally clicked the back button without advancing the dialogue not even once, than it took me back to the title screen and the options like "new game" "load" or "preferences" were all gray and i cant click my phone's back button to go back. I tried restarting the app several times and it did not go back

The last time i had this problem i had to clear my data on the app and my save files and progress were all gone.

I recently found a solution to that. i found it on android, i guess it will work on other os.

It consists of entering the Data files in the android folder, backing up the folder "com.wotb.tennisace", Copy it and paste it into another folder on the phone, either in Download or Dcim 

After you have made a backup of the folder, you just have to give the game data to delete in the settings.

When you have deleted the app data, open the app and close it, go back to the file explorer, copy the backup and paste it where it was before And that's it, you didn't lose your progress