Well, I resolved it. Sort of. The Deco mesh had terrible performance with my ZTE MF286 4G modem. With my Huawei B315 I noticed the performance was better. Then I went through and reset each Deco...

I have seven M9 plus Deco units and am experiencing constant packet losses for UDP in the mesh network. The main effect of this is that DNS resolution is extremely patchy. I've tried using the...