Disappearing Cash

I build up cash in my stores and the wad of notes appears to indicate there is cash to collect. As you can appreciate over night this can be a lot.

The program is obviously running in the background of my iPad for this to happen.

If I go to another program - and then come back to the game - the notes disappear and the stores empty without adding to the total.

I thought it was the Apple Game Centre at first causing this issue at it coincided with the "welcome back" message appearing so I disabled that but it still happens.

I'm using iOS 9.0

Thoughts?
Are you playing the same account on different devices?

If you collect money on your phone, then start the game on your tablet, it's normal the money tooltips disappear.
No - I only use the iPad Air 2 running 9.0 IOS
I paid 9900000to unlock a building site and my cash was taken but the site wasn't unlocked. Now I have to pay again WTF???????????
Francois, try to kill the app and restart it.