I attempted to trade the following items: 1. Auto MP potion pouch 2. Auto HP potion pouch 3. Winged boots 4. Prince pepe 5. Binoculars but couldn't. I am able to insert aforementioned items in the trade slots but once I click on "trade" a msg pops "unsuccessful trade". I cannot drop the items either. And yes, I do have space in my inventory.
I have done some tests with random people in FM. Turns out only nx pet items trades give "unsuccessful trade" message.