Now this is strange: I have a Raspberry Pi Zero W connected to WLAN access points, Fritz!Boxes in my case. While the Pi Zero W is switched on, my Microsoft Surface Pro 3 tablet reproducable cannot successfully communicate in the 5GHz band with these access points anymore. The SF3 shows full WLAN strenght, but most data frames go to the Ether...
I need to switch the SF3 over to 2.4GHz where it can talk to my access point without any problems. Luckily, other 5GHz devices, such as a Samsung Galaxy Tab S successfully communicate in the 5Ghz band.
Had anyone experienced similar problems with other devices when their Pi Zero Ws are switched on?