Summoned Mobs despawn after a distance


Playing Summon Necromancer and my summoned creatures despawn if i walk “away” from them. It is kinda ridicilous to summon new ones all the time even if they didnt die actually.
This problem is not a problem if i can port with an enigma but until then it is just annoying.
Is it a bug or is it intented like that because it feel just bad.