IOS background mode issue

Hi guys,

We have an issue when running the app as in background mode with ibeacon on IOS.
We have 30 beacons in the shopping mall, when we run the app in the foreground, we can get all the messages (100%) from those beacons. However, when we run it in background mode, we’re only able to get around 50% of the messages from 30 beacons.

Looking forward to hearing from experienced guys. Thanks in advanced!