This is the third time its happened, so thought I'd post and see if I'm the only one.
Three times attaching a rare item to an object, in this case a rare log to a coal pile, the roll sounds, the item attaches, and instead of getting a rare item, the list of the item I was using (in this case logs) turns rare, not the item i'm attaching to. The pile of logs weren't rare, the item header: Logs shows as blue (rare) but nothing in there seems to be rare.
It appears as if it's assigning the rare incorrectly.
This happens in cases where it's a large quantity of items in your inventory. The other time was attaching a plank to bsbs. Random rare MOI, plank attached, no rare bsb, but the item header: planks showed blue.
I was trying to remember the third one, and IIRC it involved wood products, but can't be specific.