The shroud around the hotend unfortunately seems to block some of the airflow from the right fan when you're printing really small objects (like the robot). Printing two robots at the same time (add another bot and then Tools -> Print all at once) can help as it will move the head away from one of the robots for a little while to give it a chance to cool down.
Sounds to me like a problem with the right fan. Is it running?
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