Database rebuild?  I've only played solo on it so haven't experienced that problem.

I deleted and reinstalled, and the save data was fine. However, it did nothing alleviate the crashing problem with this game. 
Do have any advice for that?

Deleting the game wlll not effect save files, however if you're worried you can back up to USB or the cloud if you have +.

Deleting the game will not touch your save files. Delete the game and redownload/install it.

I'm having the issue on Gauntlet: Slayer where the game crashes when all the players die. It happens every time.  
 
I wanted to delete the game and reinstall it, but first I want to make sure all the game data is saved and backed up for me and the other 2 users in my house. 

What's the best way to do this? 

Backing up a single game, help.