Please see factory reply:
The customer cannot reproduce the application condition at the moment of failure. A random spike was probably not recorded.
On the other hand, Vishay cannot detail if an internal defect in the capacitor internal layers was developed a moment before the failure.
Our analysis does not point on any manufacturing problem but the failure pattern indicating excess forward voltage.
In the 8D the first (Short) table describe test results after three times reflow. This is our standard sample test to verify capacitors
ability to withstand soldering heat.
We can forward the returned parts to additional two reflow cycles and advise test results
Regards
Vincent