Hey Geoff, Welcome!!! Glad to hear you are lovin your GST. This is not really a common problem but as you know with RC that high stress parts do fail... Contact CEN and they will be happy to get you the parts you need. Its most likely the spring broke, but my advise would be replace both the pin and spring!!! You can find the contact info for CEN on their website www.cenracing.com

Hope this helps some!!