I tried dropping an item but I use a 60% keyboard so it's a bit hard for me to use arrow keys. I don't know what I exactly did, but I pressed "d" to drop it and accidentally dropped a +3 knight shield that was currently equipped, and picked up 2 of the same knight shields afterwards! I managed to record it happening so I got this image of the dupe. This occurred in the downloadable version.

I tried replicating the bug but couldn't get it to work.

hummm, thanks for reporting. Tried following your steps but I was not able to replicate this bug.

I will add to the "bug list" but without more information about this, I don't think I can solve this :(

Looks like this dupe-bug is the same as double-input-bug. So this will be solved with the upcoming update :)