I was doing an iron farm in my spawn chunks and to do so i used pillagers, y brought them from a pillager outpost and gave them a nametag, but when i left the pillagers dissapeared, and the iron farm stopped working, i found that when i log out and log in again the problem was solved and the pillagers were there again, and the iron farm worked, but only if was still there, because the second i leave then the pillagers become invisible again. Note: it only happens with pillagers, zombies and other mobs that are also named work right. The pillagers are also pacifist(they dont have crossbow) because i need them that way to do the iron farm, and i did that by letting them break their crossbow.