Afk Mob farms not working on the new update (1.15)

I just updated my minecraft world (1.14.4) To new vversion launched at december 10, minecraft java 1.15 and i leaved my pc afk in my mob farm but the mobs don`t throw any item after dying and that didn´t happen on 1.14. Please reapair this bug 

 

after 2 hours afk i noticed that mobs dont drop any item of fall damage