I have killed a few robobrains now, including the one marked in the map for the quest marker for “Trade Secrets”. None of these enemies have dropped the Robobrain Interpolator, how come? What am I doing wrong?
You will need to select the item slightly different from normal item drops. You will be able to collect the Interpolator from any Robobrain enemy that you kill.
Check the options below the loot menu and you will see there is an option to to get the item. See the image below.