According to Turkish Airlines flight rules, boarding gates close no later than 20 minutes before departure time.
My wife and I have arrived at the boarding gate 22 minutes before the departure. Moreover, the shuttle bus was in front of the gate. However, they did not let us because the shuttle is already full. Also, I have a friend who had been on the same flight and successfully boarded, and he said that there were two stand-on passengers on the shuttle bus for our flight.
As a result, we have been charged nearly $890 (5600 TL) penalty in total for missing a flight also to be able to use our return booking + price difference for the next flight.
Several times, I have requested Turkish Airlines to check records of the surveillance cameras to determine our arrival time at the boarding gate. They replied they have no responsibilities on camera records. I just want to know if we really were late for boarding. They replied you were late, I am sure we were not.