Scarab not triggering map drop 402,067,398

Just finished a map with Final Map Boss will drop an additional Unique Map.
There are 0 monsters remaining and no map dropped. Also held ALT to ensure it wasn't hidden by loot filter. Attached is a screenshot with the map modifiers shown at boss with ALT held.

Are you running Singular Focus? That will block all unique maps that aren't the same base as the map you run from dropping, but I never tested if that works with the scarab.