When going through the exercises in a Creo self-guided course or certification, make sure that you not only close the models in Creo when finished with an exercise but also erase them from session memory before moving to the next exercise or question.
When you close a model in Creo, while the model itself no longer displays in the graphics window, it's still in Creo's cache, or session memory. Creo employs session memory as a way to shorten open and regeneration time of models.
Thus, if you forget to erase models from session memory and the next exercise or question has you open an assembly that has different components of the same name as the previous exercise or question, Creo simply re-opens the model that is still in session memory rather than the model on the harddrive. The net result is either failures or model geometry that does not appear as you expect it to.
Example:
Exercise 2 has you open an assembly that has a child component named BASE.PRT. You work through Exercise 2 and when you've finished it, you close the window that has the assembly and components but do not erase them from session memory.
Now, Exercise 3 has you open a totally different assembly that happens to have a totally different component also named BASE.PRT. Because BASE.PRT from Exercise 2 is still in Creo's session memory, THAT is the model that is opened, instead of the BASE.PRT component from Exercise 3.
Check out the tutorial Use Erase Not Displayed in Learning Connector for more information and picks and clicks.