Ubiquiti unifi broken ping. Why?

Question

WiFi

Greetings. There are 4 Ubiquiti unifi points and a controller on the same network. Clients constantly lose ping, the response from a node in a neighboring network can be thousands of ms, or packets simply do not reach. Ping from the point itself (SSH) to the same node is ideal, i.e. we can conclude that everything is in order with the network. I don't see anything unusual in the logs of the controller and points. Clients have a maximum signal level. I can not analyze the frequency range due to the lack of appropriate equipment. Channels changed, they do not intersect. Nearby there are no networks and points within a radius of 2-3 km. Where to dig?
Well, a screenshot for clarity: https://yadi.sk/i/_9ZjraONuP8RP