From Blueprints placed Characters can't move in nav mesh anymore, when many objects are placed inside it at BeginPlay

When I start the game and just spawn such a character from BPs, everything works. But when I start the game with generating the level (a big labyrinth), all the characters see me, but they can’t move anymore. All the nodes get executed, but nodes like “Add Movement Input” or “Simple Move to Location”, i use in the spawned-character class just don’t make the character move anymore.
Any ideas?
Thanks for answers!

Does your level yave a nav mesh and is the navigation being built

If you make level in blueprint and you want nav mesh you have to go into project settings > navigation > dynamic generation instead of static.