As many already have pointed out in many questions, there is a voltage difference of about 0.2V - 0.1V between the reported app voltage and the controller terminals voltage.
Some report its higher, some report its lower.
In my case its reporting 0.2-0.1 V LOWER than the actual voltage of the battery.
The setup is as simple as it can get.
12v system
12v Lifepo4 battery->25cm 6mm2 cable->Smart Controller
Nothing else attached or connected.
Voltages have been measured both on the MPPT battery terminals as well as on the battery itself and i have confirmed it with three different multimeters.
Possibly a firmware problem or its just "acceptable", with all the side effects that it may have (like f.e terminating bulk stage 0.2v HIGHER in reality ?)