First time I hear about this, I’m pretty sure there is no bug and the UI is just very confusing. IIRC, only items with an active effect appear in your inventory, those with passive effects like boots or guides won’t.
Thanks for the video. It’s definitely a bug, I have no idea why it does this after you scroll. Maybe it works if you scroll with the mouse wheel instead of dragging. Sadly, this game has been abandoned a long time ago and I’ve switched to a new Unity UI engine since then so I’m not going to fix it. I’ll switch the game to completely free instead (it’s not selling anyways)