Fish sold by 4.5.0 player can't be dropped from inventory

[yarite]

FT Account name: yarite
Time of bug: "Same time as post"
Where: in current game version (not beta)
What: One player meatdrapes said he got about 7 "question mark" items from other player, and now can not get rid of them. I suggested it could be new 4.5.0 items, e.g. fish and tried to reproduce on my accounts.
So yes, if I sell fish from 4.5.0 player alt, to other alt playing current version - that alt can buy the "question mark" item. But later I can not sell it. Also if I drop it, icon appears on screen like dropped item. But about minute later it returns back to inventory.
Why: I think people from current version should be able to drop beta items, to free their's inventory

[yarite]

I also tried workaround. Came to shop, dropped "uknown item" and tried to buy potion.
But it says "The backpack is full!" while showing empty spot.

[Moonraker]

Hmmmmm