The contender trigger is a set trigger mechanism. As such it is a multi lever device and there are a myriad of possible failures. It is really impossible to be certain but I'd bet the sear is not retaining the hammer, either from wear or excessive kitchen table gunsmithing. Could also be crud not allowing sear engagement or a trigger malfunction not allowing a full reset of the sear. This is almost certainly something for a smith to look at or a trip back to TC.. Good luck!!
