Cortex M1 only runs in debugger (using ARTIX-7)

Hi community, 

I'm testing a Digilent Arty devboard (containing an Artix 7 FPGA) in order to evaluate the usage of the M1 ip core. I'm following the documents/example project offered by Diligent and the video tutorial "Arm Cortex-M DesignStart FPGA getting started" offered by ARM. My setup is pretty close but not identical since I'm using a JLINK debugger.

What does work:
Pretty much everything including debugging the M1 core via Keil uVision.

What does not work:
When I upload my created bitstream the application does not start (reset button does not help). When I connect the jLink debugger now and manually start the application, the system runs as expected, e.g. sending a message via UART and flashing some LEDs when pressing buttons. If I press the boards reset button at this point, the system resets but works as expected. So it behaves like its need a kickstart from the debugger and works fine afterwards which really confuses me.

Maybe somebody can point me in the right direction?

More questions in this forum