This a WiFi channel issue. People often leave WiFi on auto channel mode. Like you said, this is fine for a single point network. For bigger networks, you’re supposed to set your channels to static and spread your bandwidth.

For example, 2.4 GHz WiFi has channels 1, 6 and 11. The in-between channels are just blending these 3. You would have one end of the network set to 1, the midpoint set to 6, and the far end set to 11. Your client device will do the work of choose the strong signal and jump between them.

If these were in Auto, they would constantly detect each other and regularly channel hop, dropping connections in the process.