It must have been REALLY loose to pull out with only a 1/4" tool. To properly retain a TTS toolholder under worst-case conditions the drawbar should be tightened to at least 25 ft-lbs. My power drawbars torque the drawbar to 30 ft-lbs using a DC motor and high-ration gearbox, and I've never once experienced pull-out, even when making the most aggressive cuts with 1/2" endmills at up to 150 IPM.

Regards,
Ray L.