apple tv loses wifi connection within one minute and cannot reconnect

Hi all,

My apple tv (3rd generation) keeps losing the wifi connection within one minute after I started to watch something (e.g. Netflix / itunes movie) and afterwards it is not able to reconnect with the wifi. Wifi works fine with other devices, so that is not the problem. Also netflix works fine on my smart TV, so that will not be the problem. Updated the apple TV several times, but did not help. Any one with a suggestion how to solve this problem?