Issues with: Grouped speakers & WiFi via multiple access points

I frequently have issues when using grouped speakers in a WiFi network with multiple access points. Whether it’s the main router device with its built-in WiFi Access Point + 1 WiFi Extender. Or the main router + a Power Line adapter. I have tried several combinations.

The issue is that:

  • Sometimes my group of speakers functions well
  • Sometimes one of the speakers is not visible, and the group is not available

WiFi configuration used
For each WiFi device that I have added (wireless Extender or Powerline Adapter), I have configured it to copy all settings from the WiFi Access Point of the main router. So it has the same SSID, password, etc.

I wonder if it might happen that one speaker connects to the Router Access Point and the other one to the WiFi Extender. And then that the speakers (Up2Stream Mini’s) detect both Access Points as different hardware (and not the same WiFi network), and therefore are not able to be grouped.

Does anyone have experience with this?
I would like to understand how to configure a WiFi network with multiple access points, in such way that the speakers always function well and as a group.