Hi PimJager!
The Estimote app unfortunately turns on very specific settings for the Estimote Location packet namely sets it to the -12 dBm.
To apply the changes a bit around, but working way is to change the settings in Estimote Cloud (they will be marked as pending) and only connect to the beacon. Upon connection the settings are synced with Estimote Cloud. You can double check it in the web panel that for that specific beacon pending settings are no longer pending 
The -12 dBm power setting is the reason of the behaviour you describe.