TFT bug with an item

Picked shivanna with spatula, combined with another spatula to have +1 slot on board, placed her on bench, bonus remained. In game (while i was fighting) i decided to sell shiv for the income, and simultaniously put item on mordekaiser which was fighting at that time. After the end of a round my bonus from an item dissapeared, varus from the board automatically returned on a bench. Tried levelling morde, swapping places, leveling up - bug didnt dissapeared. I assume if i wouldve selled morde and equipped item again i wouldve had buff, but i needed him in my teamcomp so i didnt.