Heating issue on passenger side

Hi,

i have the car listed above 1.6 CRDI Diesel European model car. It had heating issue which was fixed previously by changing blocked heater core under the dash that cost me a lot of money but it was fixed and worked for more than a year. Now issue again arise as no heat on passenger side and have mild heat on driver side I checked blend door actuator and it works fine it moved when I turn knob to heat and cold. I have added video that shows it does moves. So what is the possible issue here? I don't know. Could you please guide me on it? Thanks a lot.