Main router RT-AC87R; 2 access points configuration problem

[advil102]

Have a RT-AC87R as my main modem router and 2 access point routers a RT-AC66U and RT-N66U.

1. all are in roaming mode.
2. all keep going in the 2.4Ghz band in auto to the 6 channel on the 20Mhz except the RT-AC87 goes to the 40Mhz
3. the 5Ghz no problem there all in auto and get different channel. run in the 40mhz and 80mhz in auto.

How can I configure them to work in much better condition. sometimes I get disconnected in the middle of a video asking me to reconnect? I have 9 IP security wireless cameras that are the most problematic for me. they get disconnected especially the most distant from my home that's the main reason of having 2 access points.

 

[KGB7]

Don't use Auto setting. Manually configure channel and channel bandwidth.

 

[advil102]

My problem is that some wireless ip cameras get connected in one AP, others in the other AP and others in the main router and I can't see all of them in my phone the only I can see are the ones that get connected in the main router. The others I can see only when I'm near those AP to be in the same AP connected.