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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