I bought another router, Asus Rog GT AX6000 and unfortunately the problems are the same. After some time the tv disappears from the cast option. It seems to be stable on the guest network. :((
I have the same problem on a G2 for half a year and it is getting exhausting. The only times it seems to work better is when I connect it to a guest network created specifically for TV.
I was recommended by LG for the test to create a hotspot from another phone and to connect the TV and personal...