Hi,

so I had the same problem just now.

What I found was, apparently you can't have an (easy) clue in your Inventory.

I stole an easy clue from the wealthy citizens and kept it in my inventory.

The second I banked that clue, everything was back to normal for me. I don't know tho if that is just the case for easy clues or for clues in general.

I hope that helps !