Could you clarify if the phone keeps sticking to the RUTX WiFi, or the one provided by TP-Link devices?
Generally, for the best WiFi roaming experience, the settings of WiFi APs should be matched as closely as possible. This means:
- The same SSID;
- The same password;
- The same encryption (WPA3 is recommended);
- The same cipher;
- Make sure the nearby APs channels do not overlap;
RUTX50 supports IEEE 802.11r, which is the standard for WiFi roaming, however, TP-Link seems to use their proprietary Mesh system, so there is not much that can be done other than the recommendations mentioned above. If you are using the 2.4GHz channel, in the global 2.4GHz settings disable the option Allow legacy 802.11b rates. This will cause the device to disconnect sooner and minimize the "sticking" of the client devices.