Gear VR apk is not signed

I am launching a game from the editor and I have done all the signing stuff.
The osig file is in the 4.18/Engine/Build/Android/Java/assets folder and when I launch the game with the “configure the android manifest for development to gearVR” enabled.

When I launched the game, the app shuts down while the oculus app says:
“Thread priority security exception. Make sure APK is signed”

The weird thing is: When I launch an other project everything works. This one is also done with the 4.18 version and has the same settings.
When I launch my project without the android manifest for GearVR i can play the app without any errors.

Is it maybe because in the not working project the streamingMediaSource and the gearVr are somehow not working together?

Greetings

Evil_Fischi