Sampling-check 1pcs unit to tear down with lid and wall with cutting, the lid and Wall solder ring were covered by solder. It is no possibility that no solder or less solder caused leakage, and the EDX performed also, the solder element Sn was detected. So It highly suspect maybe unit no leakage issue and exist solder void between lid and wall, maybe the solder void changed bigger till to leakage during customer reflow caused leakage issue.