2.001 WLan switches off on Raspberry Pi2 and 3

Sometimes the Wlan connection switches off after a while
on Volumio 2 Devices.
I tried to check if it happens allways after the same time or
if it is a problem with a special Wlan transmitter fitted to the raspberry.

Now, I noticed that Volumio handles code wrong sended from my AVM Rooter.
Two Raspberry Pi2 with different Wlan transmitters and one Raspberry Pi3
stopped working at the same time when I saved a change in configuration
of the rooter. For the change no restart of the rooter or the Wlan was neccessary
and an other connected device was still playing on.

At some cases or times the rooter also sends service informations to the
connected devices (don´t know what, it´s not explained detailed in the log)
and sometimes all Raspberries with Volumio 2 stopped working at the same
time a event was written to the rooters log.

After this the LED´s of the external via USB connected Wlan transmitters
where off. Only disconnecting from power and restart helped.

There is also a discussion about a Wlan Eco Mode of AVM Rooters
which is not accessable via the rooter settings.
But in Volumio 1.55 the problem doesn´t exist.