PCE-AC68, not picking up channel 120

[Slipknot79]

Yea, as described, i cannot get connection on channel 120 (5,6GHz). I then cannot find routers session ID. For example there are no issues with channel 100.
My router sometimes changes the channel automatically to conntect on a "better" channel, it a routers feature, and sometimes its channel 120. I could choose the channel manually, but the auto-channel feature of the router works well as he finds channels unused by other clients, and so i get best WLAN-speed (i am using 250MBit internet connection).

So whats the problem with channel 120?
My smartphone connects without any problems on any channel.

I live in EU, so channels above 48 are alowed with DFS/TPC.