Descriptive flexfield on OE Order Lines All not being updated consistently - Oracle R12

We use attribute9 on oe_order_lines_all to store information on pieces remaining to ship for an order line. When we ship partial and the line splits there is a before insert trigger on oe_order_lines_all that sets attribute9 on the newly created line equal to the line it was split from minus the amount shipped. Since going to R12 the values are not always being updated, seemingly at random. Most of the time the attribute updates correctly but occasionally it reverts back to its previous value from before the trigger updated them. After the problem was reported I created an after update