We recently shipped over 250 products including the OPA2673 from Belgium into Spain by road transport (Barcelona, then further to 23 different sites). Once arrived, on all sites, 90% of the products showed degraded performance. After analysis, we found that the degradation is due to a dramatic increase in bias current on the noninverting input: while we normally measure a few microamperes (consistent with datasheet), we now measured tens of microamperes, with some devices up to 55 microamperes at 25°C, while the spec says maximum 25 microamperes. We have no idea what could have caused this shift in input bias current. All units were duly packed in anti-static bags. Some units stayed in our Belgium warehouse and are not affected. Any idea of what could cause such a bias shift over the course of a few months time?