I've got my home internet connection set up via mobile internet using a 5g antenna and standard modem/router, both provided by the ISP. 

Everything works fine when I'm using my ISP router for wifi. But after setting up my wifi with a Deco 3 piece, the antenna would switch off and back on again approx. 5-10 times a day. Especially when I turn on my PC or laptop and it connects to the deco wifi network. I've had my ISP change  both their router and the 5g antenna 2 times, and as mentioned, everything works fine when I'm using wifi via the ISP supplies router. But as soon as I turn on deco wifi, it starts messing with the antenna and everything stalls. This is especially annoying in the evening when watching TV.  
 

I've turned of dynamic DHCP on the deco, the ISP router handles IP adresses and I have reserved three IP adresses on the router for the deco mesh devices. The deco itself is in AP mode. 

If I don't fiy this the deco is going back. 

Any thoughts?