No direct experience with this particular issue....but, I do know that measuring capacitance can be tricky.
How are you arriving at this conclusion? Are you measuring the caps on the bench before assembly, and then on the boards post assembly? Capacitors in circuit nearly always measure differently than caps out of circuit, so, getting accurate readings can be difficult as they are affected by the other components around them.
If you're confident of the measurement methodology, it might be best to involve Panasonic in your investigation. It's probably worth having them do a failure analysis on the components, to help diagnose what the problem is. As long as you bought them from distribution, and not the grey market, you should be able to get a rep involved via your distributor, and get to root cause.
cheers, ..rob
reply »