App no longer connects to the internet.

I've been having a problem for two weeks where the app Brave Frontier loses connection to the internet. It requires a download off the app store, then it requires an additional installation. 14% into the download (varying occasionally, but very rarely going above 14%) it stops, and claims that 'A connection error has occured.'. Brave Frontier was the only app I had this problem on for over a week, and then later Hero Buster, another app, had a similar problem. My other game apps (Puzzle and Dragons and Dungeon Boss, for instance) work perfectly fine. I never have internet problems on anything else.

The strangest part of this is that Brave Frontier actually did successfully install the first time I downloaded it. I later had to delete it because of another issue, but when I tried to redownload it, it stopped installing properly. I've searched to see if anyone else has had this problem, and I couldn't find anything remotely recent. The app itself doesn't seem to be to blame, since none of the dedicated forums to the game discuss this issue.

I've attempted the following to try to get it to work:

- Deleted and reinstalled the app.

- Restarted my iPod.

- Ensured the date/time information is synced.

- Modified my DNS server.

- Reset my network settings.

The only other suggestion that I've found is a full factory reset, but I can't do that without losing my data on my other apps, since for some reason iTunes doesn't seem to be making backups of my iPod properly (though that is a question for another time). Is there anything else that I might be able to do to try to get these apps to work?

I am using an iPod Touch 6th generation with iOS 9.2.1 (this problem occurred both before and after upgrading).