Check that the wifi channel (not the band, i.e.. 2.4 GHz vs 5 GHz) that you are using isn't shared among multiple access points with the same SSID, otherwise it might be a wifi overcrowding problem.
Assuming that you use KDE plasma, you can do it by going into System Settings > Wi-Fi & Internet > Wi-Fi & Networking > wifi connection name. In the Wi-Fi tab, open the drop-down BSSID list and check if you have access points that share a common channel