Solved: Some sounds are not playing in the build?

Hi, I just ran into a strange issue regarding my packaged game. Everything works fine in editor, but in the build the footstep-sounds and the jump-sound of the player character are not playing. Footsteps of AI are playing as well as any other sound. What could cause that? Already checked the output-log, but there’s no entry regarding those sounds.

Edit: The sounds are there, but much more quiet than in the editor.