I have a Zigbee Network using SONOFF “SONOFF Zigbee 3.0 USB-Dongle”. The devices are properly connected and are working. My only problem is, that range extending seems to not work properly. When you look at following image, you can see that “Waschraum Trockner Plug” has good connection to “Lampe Treppenhaus” which has good connection to the Coordinator. “Humidity Waschraum” is in the same room as “Waschraum Trockner Plug” and “Waschraum Lüfter Plug”. But it does not connect to them. “Waschraum Trockner Plug” is a SONOFF SNZB-02.
Agree with @Mats789, if it’s working, don’t worry about it.
The end device decides which router to use.
Some end devices can be very sticky and not re-route when they should, some will change with the breeze, some seem to choose nonsensical routes.
The sensor may think coordinator is closer than it really is. Unless you have changed the default, the coordinator signal is amplified +5db or +9db depending on fw revision. The boosted coordinator signal may appear stronger than the nearby, unamplified signal of the plug.
You can always try re-pairing directly via the desired router device and see if it sticks, but don’t be surprised if the end device eventually moves itself back.