One of the radiators was getting warm even though the Heating has been set to OFF. Couldn't explain that because the only thing that is firing the boiler is a Hot Water top up schedule. The TRV displayed the Heating Off setpoint of 5C. Looked at the controller and it seems that particular radiator's valve has a low battery.
So have I just stumbled on some kind of fail safe feature where the TRV valve will be opened up in case of a low battery situation. Or is this some new feature of the firmware that can open the TRV (via a Heat Demand) but still keep the Heating Off set point.
I previously thought someone must have manually turned the knob and we know that the new firmware does not allow the boiler to fire with a manual override when the Heating is set to OFF. However there is an associated new bug where the Heating OFF set points aren't being resent so the TRVs stay open and will heat up whenever there is hot water in the circuit.
But in my case the Set point displayed on the radiator valve was showing 5C and yet the radiator was hearing up.