Old WW11 fighters were more prone to this. A taildrgger aircraft, especially because of the nose high attitude, resulted in more thrust been produced on the downgoing blade than the upgoing blade. Therefore if they were to gun it on takeoff (low speed, reduced airflow over the tail / rudder, high thrust) - they wouldnt be able to control the yaw with the rudder and thus groundloop.

Some full size aircraft such as Cubs, Tigermoths etc didnt have brakes, therefore if they were going to run into the fence on landing they would intentionally grounloop to stop.

Model engines turn clockwise when looking from the rear, so a sudden increase in power at low speed will more than likely cause a yaw to the left. Compensate with right rudder at the start of the takeoff roll, and reduce as airspeed incresaes. See if that works.