Electrical issues - horn, odometer, info display, radio lights
 

I recently purchased a pre-owned 2012 Mazda3 i Grand Touring hatchback.

The horn works intermittently.
The odometer, information display above the console, and the blue lights around the radio come on sometimes when I open the door (before I put the key in the ignition).
The key fobs have been working intermittently, too.

Is this a known issue? Something a fuse can fix? Grounding issue with the electrical system?