Core Shift Analysis predicts the effect of the melt-front on mold inserts and part inserts. This may be used to determine if core deflection results in modified thicknesses in the part or possibly even breakage due to fatigue.
To see a summary look at this article in MoldMaking Technology:
Depending on gate location, length of core and injection pressure some surprising beefy cores can shift. This defect is most obvious when wall thicknesses on molded parts come out thinner or thicker than designed.