Yes, it was in fact the compression stack. At the moment i have yet to get the screw free from the expander wedge. What would you recommend? Theres a star nut on the way but if i lubricated the threads on the screw and was sure to clean the contact surfaces of the expander and the steerer tube would there be a problem re-using it? I think it failed due to a combination of the threads oxidizing together and a lack of friction between the compression stack and the steerer tube. (grease?) what's the recommended surface treatment between the two?