First of all you should check if your device hasn't physically left the range of the beacon.
You can check characteristic ranges for each of the TX Power values here. Please note that the expected range in meters can vary.
If you are in close proximity to the beacon and still receiving multiple notifications about entering the region check the ProximityManager configuration.
The most common problem is when choosing MONITORING in scanPeriod with interval more than 10 seconds and activityCheckConfiguration to DEFAULT.
By default activityCheckConfiguration after 10 seconds of beacon inactivity forgets about it's presence. When we set interval between monitoring to for example 20 seconds, we will be abandoning the region each time the activityCheckConfiguration's inactivityTimeout will elapse.
It is possible to simulate the 'Enter' and 'Exit' of the region or namespace by removing the battery from all your beacons and then, simply place it back in for only one of them. We recommend to use one battery beacons, to perform such tests, since they are easier to remove.
Check also our GitHub example here.