Just a suggestion - if this is a multilayer PCB it cold be that you have a batch
(since there is some PCB fabdatecode correlation and not a previously
common fault) where the lay-up has been done asymmetrically and one or
more pre-preg layers have been placed 90deg out to normal build (ie thay
have a glass warp and weft direction imbalance in the build.) This would tend
to cause more overall PCB bow and twist than usual during the soldering
procress and subject larger part solder joints like this to higher stress
Nigel
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