I used the asset

WW2 Crew Weapon Granatwerfer 36 Demo

from the Unity Asset Store.

  https://assetstore.unity.com/packages/3d/characters/ww2-crew-weapon-granatwerfer...

When I attempted to make the soldier character from the asset into a prefab, I encountered an error. The solution was to keep the german soldier gameobject in the scene all the time and not make it into a prefab.