I am working with Motion Analysis motion studies and I am generally able to build a study that works properly.  I continue to add motors and tasks and it continues to be successful.  Then I realize that I would like to add an additional feature like another actuator or another part that will help accomplish what I am after.  Once I add the new component (a part or assembly to the top level assembly) the study will no longer run the calculations.  I click "calculate" and the screen "flashes" and then nothing.  It won't run the study at all.  I check for interferences, redundant mates, etc. and everything checks out.

I have been having this issue for months on various different studies.  Every time I try to add a component it no longer works and I have to rebuild the study from scratch - meaning I have to make a new study - I can't use a duplicate study.  I simply rebuild the study EXACTLY as it was built previously when it wouldn't work, and now it works again.  It takes so much time to completely rebuild the study time after time.

Does anyone have this similar experience - what am I missing?  Why is this happening?