Problem With H2G2 Remake - Dropping

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Hi guys,

I am in the middle of playing the Hitch Hikers Guide To The Galaxy Remake and I know I need to drop a particular item in order to progress in the game, but for some reason the "drop"  option normally present when clicking on items in the inventory has disappeared completely! I have been playing this infuriating game for ages and am getting quite frustrated! I was wondering if anyone else has played it and knows what is going on? 

Sorry, I know this question is very specific.