ZoneHVAC:Baseboard:RadiantConvective:Water model inlet temperature different than node temperature

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I am baffled by this problem and didn't find anyone mentioning it before. In my model (E+ v8.9), the water radiator is connected in the following branch with hot water inlet and outlet nodes:

Branch,
OT:Zone Water Radiator ASHP Loop Demand Side Branch,        !- Name
,       !- Pressure Drop Curve Name
ZoneHVAC:Baseboard:RadiantConvective:Water,     !- Component 1 Object Type
OT:Zone Water Radiator,     !- Component 1 Name
OT:Zone Water Radiator Hot Water Inlet Node,        !- Component 1 Inlet Node Name
OT:Zone Water Radiator Hot Water Outlet Node;       !- Component 1 Outlet Node Name

However, the simulation result shows the radiator's water inlet temperature jumps to 75°C from about 48°C at the inlet node when there is water flow. See the chart below. The flow rate readings and the outlet temperature match between the radiator and nodes, though. It looks as if ~2kW heat has been added. Can anyone suggest a possible cause of this?

The full model is here: https://files.jeplus.org/UnmetHours-2...

Thanks,

Yi