Deco X5700s

I have 3 X5700's installed using wired ethernet backhaul between them. I tried to enable the IoT network, but it appears that just runs on the main router and not the satellites - which won't work for me. So I enabled the guest network instead, forced it to 2.4g and treated it like an IOT network. But I kept seeing random dropouts on it.

My 3d printer wouldn't stay connected. Enable 2.4g on the main wifi, and it works fine there.

Still having signal instability on the 2.4/Guest side.

I ran network optimization and it said the wifi interference was perfect.

Any ideas?