OK, so you have not tried reverting to 1005. That should be your next step. If you revert to 1005 and the problem goes away, then upgrade to 1006 again and it comes back, then you were definitely right, 1006 caused the issue. If you revert to 1005 and the problem remains then your assumption that 1006 caused the problem is proven to be false and you can start considering other possibilities.