This is the same terminal where the EOS occurred. There are multiple cracks on the capacitor near the bottom. This is due to board flexing, however, the solder does not wet the terminal metal to form a continuous interface leaving a good connection.
The four arrows point toward cracks in the bottom margin area of the capacitor. The fourth arrow from the left, if one follows that crackdown, it ends where the solder first makes a continuous interface to the terminal metal and goes around the corner and ends at the first electrode, where the void is shown by the blue arrow. In the end, this was caused by a poor manufacturing process, however, the engineers wanted to blame the component manufacturer. This resulted in review of solder fluxing procedure and solder temperature monitoring.
Failure analysis is always done with the intention that corrective action will eliminate or minimize the exposure to the customer. Gideon Analytical Labs (GAL) has been involved with finding the root causes of many problems affecting materials, packaging, moisture, ionics, compatibility, handling, manufacturing, process improvements, new technologies, different test methods, etc.. GAL has found that our analysis beats the competition and our results when implemented solve the problem. These are the words of our customers because they have gone to several labs that never have a concrete answer and the results are inconclusive. Why spend the money? Use Gideon Analytical Labs in the first place.