Bug: Items "stuck" in inventory

[Ouka]

I just talked to Mickey to start the quest where he asks you to plant stuff for fruit salad and because my inventory was full I had to drop a couple of items. I started and selected one and then decided to go cancel and just sell them and come back. When I open my inventory, the picture of the item I had initially selected is still there and the slot is used, but I can neither sell nor drop it.
When trying to drop it I get a message saying I can't drop any items here and when trying to sell it there's an error claiming I don't have enough items.

[BlondeBomber2U]

I've been stuck on Mickey's quest. It's ready but he's stuck on repeating the same thing over and over. Same with the other quests. I've finished a few but now all quests are stuck.