When a head trigger, Roland or any other brand/build, isn’t performing like it “used to,” it is because one or both components have degraded and no longer deliver the triggering performance it used to.  These two components in a any head trigger system is a ceramic piezo (27mm or 35mm in diameter) and a foam cone (or other shaped foam energy transfer interface). 

These components break down with use (normal wear-n-tear) or damage.